Coated articles with optical coatings having residual compressive stress

ABSTRACT

Disclosed herein are coated articles which may include a substrate and an optical coating that includes one or more layers of deposited material. At least a portion of the optical coating may include a residual compressive stress of more than 100 MPa. The coated article may include a strain-to-failure of 0.4% or more as measured by a Ring-on-Ring Tensile Testing Procedure. The optical coating may include a maximum hardness of 8 GPa or more and an average photopic transmission of 50% or greater.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 16/474,388, filed on Jun. 27, 2019, nowU.S. Pat. No. 11,242,280, which claims the benefit of priority under 35U.S.C. § 371 of International Application No. PCT/US17/67332, filed Dec.19, 2017, which claims the benefit of priority under 35 U.S.C. § 119 ofU.S. Provisional Patent Application Ser. No. 62/440,682 filed on Dec.30, 2016, the content of each of which is relied upon and incorporatedherein by reference in its entirety.

BACKGROUND Field

This disclosure relates to durable and/or scratch-resistant articles andmethods for making the same, and more particularly to durable and/orscratch-resistant optical coatings on transparent substrates.

Technical Background

Cover articles are often used to protect devices within electronicproducts, to provide a user interface for input and/or display, and/ormany other functions. Such products include mobile devices, such assmart phones, wearables (e.g. watches), mp3 players, and computertablets. Cover articles also include architectural articles,transportation articles (e.g., articles used in automotive applications,trains, aircraft, sea craft, etc.), appliance articles, or any articlethat benefits from some transparency, scratch-resistance, abrasionresistance, or a combination thereof. These applications often demandscratch-resistance and strong optical performance characteristics, interms of maximum light transmittance and minimum reflectance.Furthermore, some cover applications benefit from a color exhibited orperceived, in reflection and/or transmission, that does not changeappreciably as the viewing angle is changed. In display applications,this is because, if the color in reflection or transmission changes withviewing angle to an appreciable degree, the user of the product willperceive a change in color or brightness of the display, which candiminish the perceived quality of the display. In other applications,changes in color may negatively impact the aesthetic look or otherfunctions of the device.

The optical performance of cover articles can be improved by usingvarious anti-reflective coatings; however known anti-reflective coatingsare susceptible to wear or abrasion. Such abrasion can compromise anyoptical performance improvements achieved by the anti-reflectivecoating. Abrasion damage can include reciprocating sliding contact fromcounter face objects (e.g., fingers). In addition, abrasion damage cangenerate heat, which can degrade chemical bonds in the film materialsand cause flaking and other types of damage to the cover glass. Sinceabrasion damage is often experienced over a longer term than the singleevents that cause scratches, the coating materials experiencing abrasiondamage can also oxidize, which can further degrades the durability ofthe coating.

Known anti-reflective coatings are also susceptible to scratch damageand, often, are even more susceptible to scratch damage than theunderlying substrates on which such coatings are disposed. In someinstances, a significant portion of such scratch damage includesmicroductile scratches, which typically include a single groove in amaterial having extended length and with depths in the range from about100 nm to about 500 nm. Microductile scratches may be accompanied byother types of visible damage, such as sub-surface cracking, frictivecracking, chipping and/or wear. Evidence suggests that a majority ofsuch scratches and other visible damage is caused by sharp contact thatoccurs in a single contact event. Once a significant scratch appears onthe cover substrate, the appearance of the article is degraded since thescratch causes an increase in light scattering, which may causesignificant reduction in brightness, clarity and contrast of images onthe display. Significant scratches can also affect the accuracy andreliability of articles including touch sensitive displays. Single eventscratch damage can be contrasted with abrasion damage. Single eventscratch damage is not caused by multiple contact events, such asreciprocating sliding contact from hard counter face objects (e.g.,sand, gravel and sandpaper), nor does it typically generate heat, whichcan degrade chemical bonds in the film materials and cause flaking andother types of damage. In addition, single event scratching typicallydoes not cause oxidization or involve the same conditions that causeabrasion damage and therefore, the solutions often utilized to preventabrasion damage may not also prevent scratches. Moreover, known scratchand abrasion damage solutions often compromise the optical properties.

SUMMARY

According to some embodiments, a coated article may comprise a substratehaving a major surface, and an optical coating disposed on the majorsurface of the substrate and forming an air-side surface. The opticalcoating may comprise one or more layers of deposited material. At leasta portion of the optical coating may comprise a residual compressivestress of about 50 MPa or more. The coated article may have astrain-to-failure of about 0.5% or more as measured by a Ring-on-RingTensile Testing Procedure. The coated article may have an averagephotopic transmission of about 80% or greater.

According to some embodiments, a method for making a coated article maycomprise depositing an optical coating onto a major surface of atransparent substrate. The optical coating may form an air-side surfaceand comprise one or more layers of deposited material. At least aportion of the optical coating may comprise a residual compressivestress of about 50 MPa or more. The coated article may have astrain-to-failure of about 0.5% or more as measured by a Ring-on-RingTensile Testing Procedure. The coated article may have an averagephotopic transmission of about 80% or greater.

Embodiment 1. A coated article comprising:

a substrate comprising a major surface;

an optical coating disposed on the major surface of the substrate andforming an air-side surface, the optical coating comprising one or morelayers of deposited material;

wherein:

at least a portion of the optical coating comprises a residualcompressive stress of more than about 50 MPa;

the optical coating comprises a strain-to-failure of about 0.4% or moreas measured by a Ring-on-Ring Tensile Testing Procedure;

the optical coating comprises a maximum hardness of 12 GPa or more asmeasured on the air-side surface by a Berkovich Indenter Hardness Testalong an indentation depth of about 50 nm and greater; and

the coated article comprises an average photopic transmission of about80% or greater.

Embodiment 2. The coated article of embodiment 1, wherein one of:

(i) the optical coating comprises: a thickness of from about 350 nm toless than about 600 nm; a strain to failure greater than about 0.65%;and a maximum hardness of 14 GPa or more; and

(ii) the optical coating comprises: a thickness of about 600 nm or more;a coating strain to failure greater than about 0.4%; and a maximumhardness of 13 GPa or more.

Embodiment 3. The coated article of embodiment 1 or embodiment 2,wherein the portion of the optical coating having the residual stressfurther comprises a plurality of ion-exchangeable metal ions and aplurality of ion-exchanged metal ions, the ion-exchanged metal ionscomprising an atomic radius larger than the atomic radius of theion-exchangeable metal ions.

Embodiment 4. The coated article of embodiment 1 or embodiment 2,wherein the residual compressive stress is imparted on the opticalcoating by mechanical blasting.

Embodiment 5. The coated article of embodiment 1 or embodiment 2,wherein the at least a portion of the optical coating has a coefficientof thermal expansion and the substrate has a coefficient of thermalexpansion, wherein the substrate comprises a greater coefficient ofthermal expansion than does the at least a portion of the opticalcoating, wherein the coefficients of thermal expansion are measured overa temperature range of from about 20° C. to about 300° C.

Embodiment 6. The coated article of embodiment 5, wherein the ratio ofthe coefficient of thermal expansion of the substrate to the coefficientof thermal expansion of the at least a portion of the optical coating isabout 1.2:1 or more.

Embodiment 7. The coated article of any one of embodiments 1-6, whereinthe coated article exhibits a maximum hardness of about 14 GPa orgreater as measured on the air-side surface by a Berkovich IndenterHardness Test along an indentation depth of about 50 nm and greater.

Embodiment 8. The coated article of any one of embodiments 1-7, whereinthe substrate comprises an amorphous substrate or a crystallinesubstrate.

Embodiment 9. A method for making a coated article, the methodcomprising:

depositing an optical coating onto a major surface of a substrate, theoptical coating forming an air-side surface and comprising one or morelayers of deposited material;

wherein:

at least a portion of the optical coating comprises a residualcompressive stress of more than about 50 MPa;

the optical coating comprises a strain-to-failure of about 0.4% or moreas measured by a Ring-on-Ring Tensile Testing Procedure;

the optical coating comprises a maximum hardness of 12 GPa or more asmeasured on the air-side surface by a Berkovich Indenter Hardness Testalong an indentation depth of about 50 nm and greater; and

the coated article comprises an average photopic transmission of about80% or greater.

Embodiment 10. The method of embodiment 9, wherein one of:

(i) the optical coating comprises: a thickness of from about 350 nm toless than about 600 nm; a strain to failure greater than about 0.65%;and a maximum hardness of 14 GPa or more; and

(ii) the optical coating comprises: a thickness of about 600 nm or more;a coating strain to failure greater than about 0.4%; and a maximumhardness of 13 GPa or more.

Embodiment 11. The method of embodiment 9 or embodiment 10, furthercomprising imparting residual compressive stress on the optical coatingby ion-exchange processing the deposited optical coating.

Embodiment 12. The method of embodiment 11, wherein the ion-exchangeprocessing comprises contacting the optical coating with an ionic saltbath.

Embodiment 13. The method of embodiment 11 or embodiment 12, wherein theion-exchange processing comprises field-assisted ion-exchange.

Embodiment 14. The method of embodiment 9 or embodiment 10, furthercomprising imparting residual compressive stress on the optical coatingby mechanical blasting.

Embodiment 15. The method of embodiment 9 or embodiment 10, furthercomprising:

deforming the substrate under physical stress prior to the deposition ofthe optical coating; and

allowing the deformed substrate to reshape itself following thedeposition of the optical coating;

wherein the optical coating is deposited onto a deformed substrate.

Embodiment 16. The method of embodiment 9 or embodiment 10, furthercomprising disposing the a portion of the optical coating on thesubstrate, heating the substrate, and allowing the substrate to coolwith the coating disposed thereon.

Embodiment 17. The method of any one of embodiments 9-16, wherein thecoated article exhibits a maximum hardness of about 14 GPa or greater asmeasured on the air-side surface by a Berkovich Indenter Hardness Testalong an indentation depth of about 50 nm and greater.

Embodiment 18. A consumer electronic product, having: a housing having afront surface, a back surface and side surfaces; electrical componentsprovided at least partially within the housing, the electricalcomponents including at least a controller, a memory, and a display, thedisplay being provided at or adjacent the front surface of the housing;and a cover glass disposed over the display, wherein at least one of aportion of the housing or the cover glass comprises the coated articleof any one of embodiments 1-8.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings. It is to beunderstood that various features disclosed in this specification and inthe drawings can be used in any and all combinations.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiments, and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of a coated article,according to one or more embodiments described herein;

FIG. 2 is a schematic cross-sectional side view of a coated article,according to one or more embodiments described herein;

FIG. 3 is a schematic cross-sectional side view of a coated article,according to one or more embodiments described herein;

FIG. 4 graphically depicts the refractive index as a function ofthickness of an optical coating, according to one or more embodimentsdescribed herein;

FIG. 5 schematically depicts a cross-sectional side view of aring-on-ring mechanical testing device utilized to measure thestrain-to-failure for a coated article, according to one or moreembodiments described herein; and

FIG. 6 depicts a photographic image of a coated article following aRing-on-Ring Tensile Testing Procedure with optical coating failure,according to one or more embodiments described herein.

FIG. 7A is a plan view of an exemplary electronic device incorporatingany of the articles disclosed herein.

FIG. 7B is a perspective view of the exemplary electronic device of FIG.7A.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. Described herein areembodiments of coated articles which include substrates and opticalcoatings which have relatively high hardness, have desirable opticalproperties, and have a relatively high strain-to-failure value whenexposed to a flexural load. Optical coatings which have high hardnessmay be deposited upon substrates (e.g., transparent substrates, or glasssubstrates; as used herein the term “glass” is meant to include anymaterial made at least partially of glass, including glass andglass-ceramics.) to protect the surface of the transparent substratefrom abrasion or scratch damage. However, under flexural loads (e.g.,bending of the transparent substrate), while some transparent substratesmay be suited to withstand such flexural loads, the optical coatings maybe susceptible to damage such as cracking. For example, when placedunder a flexural load (i.e., physically deformed in some way), a coatedarticle may exhibit cracking in the relatively brittle coating while thesubstrate remains largely intact. Damage to the hard optical coating maybe especially prevalent for relatively thick optical coatings, such asthose having a thickness of greater than about 500 nm, or a thickness of1 micron or greater. This damage can be readily visible, especially forthicker coatings, and can disrupt the appearance and/or function of thedevice even if the substrate remains intact. In some cases, the coatingfailure can occur simultaneously with the substrate failure, meaningboth failure values are the same. In either case, it is desirable tohave a higher value of coating failure strain. Therefore, it isdesirable to utilize optical coatings which are not damaged underflexural loads but have good optical characteristics and high hardness.Damage to a coated substrate, or a coating on a substrate, can becharacterized by a strain-to-failure value, which is discussed in detailherein. In one or more embodiments, the coated articles may have goodoptical characteristics, such as low reflectance, while exhibitingrelatively high hardness, such as 12 GPa or greater (for example 13 GPaor greater, 14 GPa or greater, 15 GPa or greater, 16 GPa or greater, 17GPa or greater, 18 GPa or greater, 19 GPa or greater, 20 GPa or greater,and all ranges and sub-ranges between the foregoing values), andrelatively high strain-to-failure, such as 0.5% or greater (for example0.6% or greater, 0.7% or greater, 0.8% or greater, 0.9% or greater, andall ranges and sub-ranges between the foregoing values).

In one or more embodiments, the optical coating, or at least a portionof the optical coating (e.g., one or more layers of the optical coating)may have a relatively high residual stress. As used herein, “residualcompressive stress” refers to compressive stresses remaining in theoptical coating after fabrication of the coating. As used herein theresidual compressive stress is measured as follows. The desired coatingis deposited onto a substrate. A surface profiler is used to measure thecurvature of the sample, as induced by the coating. The Stoney equation,as known in the art, is then used to convert the curvature (or warp) ofthe sample into a stress value Without being bound by theory, it isbelieved that introduced residual compressive stress in at least aportion of the coating may increase the strain-to-failure of the coatingor the coated article. The residual compressive stress may be introducedinto the optical coating by various methods which are disclosed herein.For example, without being bound by theory, it is contemplated thatresidual compressive stress may be introduced to an optical coating, orportion of an optical coating, by utilizing particular depositionparameters (e.g., pressure, rate, ion-assist), by utilizing anion-exchange process, by utilizing an ion-implantation process, byutilizing a mechanical blasting process, by depositing the opticalcoating onto a deformed substrate under physical stress and thenallowing the deformed substrate to remove stress by reshaping itself(and thus introducing stress into the optical coating), or by increasingthe difference in the linear coefficient of thermal expansion (“CTE”)between the optical coating and the substrate so that residualcompressive stress is increased as the coated article is cooled to roomtemperature. The CTE over the temperature range of 20° C. to 300° C. isexpressed in terms of ppm/K and was determined using a push-roddilatometer in accordance with ASTM E228-11. These processes andconfigurations will be explained in greater detail herein with referenceto coated articles. It should be understood that the present embodimentsof coated articles are not limited to those produced by particularmethods and configurations disclosed herein, but rather the methods andconfigurations disclosed herein for forming high levels of compressivestress are examples of suitable techniques for achieving high residualcompressive stress coatings which may have relatively highstrain-to-failure values. For example, in one or more embodiments, atleast a portion of one or more layers of the optical coating may have aresidual compressive stress of about 50 MPa or more, about 75 MPa ormore, about 100 MPa or more, about 200 MPa or more, about 500 MPa ormore, or even about 1000 MPa or more, and all ranges and sub-rangesbetween the foregoing values.

Referring to FIG. 1 , a coated article 100 according to one or moreembodiments may include a substrate 110, and an optical coating 120disposed on the substrate 110. The substrate 110 includes opposing majorsurfaces 112, 114 and opposing minor surfaces 116, 118. The opticalcoating 120 is shown in FIG. 1 as disposed on a first opposing majorsurface 112; however, the optical coating 120 may be disposed on thesecond opposing major surface 114 and/or one or both of the opposingminor surfaces 116, 118, in addition to or instead of being disposed onthe first opposing major surface 112. The optical coating 120 forms anair-side surface 122.

The optical coating 120 includes at least one layer of at least onematerial. The term “layer” may include a single layer or may include oneor more sub-layers. Such sub-layers may be in direct contact with oneanother. The sub-layers may be formed from the same material or two ormore different materials. In one or more alternative embodiments, suchsub-layers may have intervening layers of different materials disposedtherebetween. In one or more embodiments, a layer may include one ormore contiguous and uninterrupted layers and/or one or morediscontinuous and interrupted layers (i.e., a layer having differentmaterials formed adjacent to one another). A layer or sub-layer may beformed by any known method in the art, including discrete deposition orcontinuous deposition processes. In one or more embodiments, the layermay be formed using only continuous deposition processes, or,alternatively, only discrete deposition processes.

As used herein, the term “dispose” includes coating, depositing, and/orforming a material onto a surface using any known or to be developedmethod in the art. The disposed material may constitute a layer, asdefined herein. As used herein, the phrase “disposed on” includesforming a material onto a surface such that the material is in directcontact with the surface, or alternatively includes embodiments wherethe material is formed on a surface with one or more interveningmaterial(s) disposed between material and the surface. The interveningmaterial(s) may constitute a layer, as defined herein.

The optical coating 120 may have thickness of from about 100 nm to about10 microns, For example, the optical coating may have a thicknessgreater than or equal to about 200 nm, 300 nm, 400 nm, 500 nm, 600 nm,700 nm, 800 nm, 900 nm, 1 micron, 2 microns, 3 microns, 4 microns, 5microns, 6 microns, 7 microns, or even 8 microns, and less than or equalto about 10 microns, and any ranges and sub-ranges between the foregoingvalues.

In one or more embodiments, the optical coating 120 may include, orconsist of, a scratch-resistant layer 150. FIG. 1 depicts an opticalcoating which consists of a scratch-resistant layer. However, in otherembodiments, additional layers may be provided in the optical coating,as are described herein. According to some embodiments, thescratch-resistant layer 150 may comprise one or more materials chosenfrom Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, AlN, Si₃N₄, AlO_(x)N_(y),SiO_(x)N_(y), SiN_(x), SiN_(x):H_(y), HfO₂, TiO₂, ZrO₂, Y₂O₃, Al₂O₃,MoO₃, diamond-like carbon, or combinations thereof. Exemplary materialsused in the scratch-resistant layer 150 may include an inorganiccarbide, nitride, oxide, diamond-like material, or combination thereof.Examples of suitable materials for the scratch-resistant layer 150include metal oxides, metal nitrides, metal oxynitride, metal carbides,metal oxycarbides, and/or combinations thereof. Exemplary metals includeB, Al, Si, Ti, V, Cr, Y, Zr, Nb, Mo, Sn, Hf, Ta and W. Specific examplesof materials that may be utilized in the scratch-resistant layer 150 mayinclude Al₂O₃, AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y),Si_(u)Al_(v)O_(x)N_(y), diamond, diamond-like carbon, Si_(x)C_(y),Si_(x)O_(y)Cz, ZrO₂, TiO_(x)N_(y), and combinations thereof. Thescratch-resistant layer 150 may also comprise nanocomposite materials,or materials with a controlled microstructure, to improve hardness,toughness, or abrasion/wear resistance. For example thescratch-resistant layer 150 may comprise nanocrystallites in the sizerange from about 5 nm to about 30 nm. In embodiments, thescratch-resistant layer 150 may comprise transformation-toughenedzirconia, partially stabilized zirconia, or zirconia-toughened alumina.In some embodiments, the scratch-resistant layer 150 exhibits a fracturetoughness value greater than about 1 MPa√m and simultaneously exhibits ahardness value greater than about 8 GPa.

In one or more embodiments, the scratch-resistant layer 150 may comprisea compositional gradient. For example, a scratch-resistant layer 150 mayinclude a compositional gradient of Si_(u)Al_(v)O_(x)N_(y) where theconcentration of any one or more of Si, Al, O and N are varied toincrease or decrease the refractive index. The refractive index gradientmay also be formed using porosity. Such gradients are more fullydescribed in U.S. patent application Ser. No. 14/262,224, entitled“Scratch-Resistant Articles with a Gradient Layer”, filed on Apr. 28,2014, which is hereby incorporated by reference in its entirety.

In one or more embodiments, as shown in FIG. 2 , the optical coating 120may include an anti-reflective coating 130 which may include a pluralityof layers (130A, 130B). In one or more embodiments, the anti-reflectivecoating 130 may include a period 132 comprising two layers, such as alow RI layer 130A and a high RI layer 130B. As shown in FIG. 2 , theanti-reflective coating 130 may include a plurality of periods 132. Inother embodiments, a single period may include three layers such as alow RI layer, a medium RI layer, and a high RI layer. Throughout thisdisclosure, it should be understood that FIG. 2 is an example of someembodiments of an optical coating 120 having periods 132 and that thatthe properties (e.g., color, hardness, etc.) and materials of theoptical coatings 120 described herein should not be limited to theembodiments of FIG. 1 or FIG. 2 .

As used herein, the terms “low RI”, “high RI” and “medium RI” refer tothe relative values for the refractive index (“RI”) to one another(i.e., low RI<medium RI<high RI). In one or more embodiments, the term“low RI”, when used with the low RI layer, includes a range from about1.3 to about 1.7 or 1.75, and any ranges and sub-ranges between theforegoing values. In one or more embodiments, the term “high RI”, whenused with the high RI layer, includes a range from about 1.7 to about2.5 (e.g., about 1.85 or greater), and any ranges and sub-ranges betweenthe foregoing values. In one or more embodiments, the term “medium RI”,when used with a third layer of a period, includes a range from about1.55 to about 1.8, and any ranges and sub-ranges between the foregoingvalues. In some embodiments, the ranges for low RI, high RI, and/ormedium RI may overlap; however, in most instances, the layers of theanti-reflective coating 130 have the general relationship regarding RIof: low RI<medium RI<high RI (where “medium RI” is applicable in thecase of a three layer period). In one or more embodiments, thedifference in the refractive index of the low RI layer and the high RIlayer may be about 0.01 or greater, about 0.05 or greater, about 0.1 orgreater, or even about 0.2 or greater, and any ranges and sub-rangesbetween the foregoing values.

For example, in FIG. 2 the period 132 may include a low RI layer 130Aand a high RI layer 130B. When a plurality of periods are included inthe optical coating 120, the low RI layers 130A (designated as “L”) andthe high RI layers 130B (designated as “H”) alternate in the followingsequence of layers: L/H/L/H . . . or H/L/H/L . . . , such that the lowRI layers and the high RI layers alternate along the physical thicknessof the optical coating 120. In the embodiments depicted in FIG. 2 , theanti-reflective coating 130 includes four periods 132, where each period132 includes a low RI layer 130A and a high RI layer 130B. In someembodiments, the anti-reflective coating 130 may include up to 25periods. For example, the anti-reflective coating 130 may include fromabout 2 to about 20 periods, from about 2 to about 15 periods, fromabout 2 to about 10 periods, from about 2 to about 12 periods, fromabout 3 to about 8 periods, or from about 3 to about 6 periods, forexample, 3 periods, 4 periods, 5 periods, 6 periods, 7 periods, 8periods, 9 periods, 10 periods, 11 periods, 12 periods, 13 periods, 14periods, 15 periods, 16 periods, 17 periods, 18 periods, 19 periods, 20periods, 21 periods, 22 periods, 23 periods, 24 periods, 25 periods, andany ranges and sub-ranges between the foregoing values.

Example materials suitable for use in the anti-reflective coating 130include, without limitation, SiO₂, Al₂O₃, GeO₂, SiO, AlOxNy, AlN,SiN_(x), SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, TiO₂, ZrO₂,TiN, MgO, MgF₂, BaF₂, CaF₂, SnO₂, HfO₂, Y₂O₃, MoO₃, DyF₃, YbF₃, YF₃,CeF₃, polymers, fluoropolymers, plasma-polymerized polymers, siloxanepolymers, silsesquioxanes, polyimides, fluorinated polyimides,polyetherimide, polyethersulfone, polyphenylsulfone, polycarbonate,polyethylene terephthalate, polyethylene naphthalate, acrylic polymers,urethane polymers, polymethylmethacrylate, other materials cited belowas suitable for use in a scratch-resistant layer, and other materialsknown in the art. Some examples of suitable materials for use in a lowRI layer 130A include, without limitation, SiO₂, Al₂O₃, GeO₂, SiO,AlO_(x)N_(y), SiO_(x)N_(y), MgO, MgAl₂O₄, MgF₂, BaF₂, CaF₂, DyF₃, YbF₃,YF₃, and CeF₃. The nitrogen content of the materials for use in a low RIlayer 130A may be minimized (e.g., in materials such as Al₂O₃ andMgAl₂O₄). Some examples of suitable materials for use in a high RI layer130B include, without limitation, Si_(u)Al_(y)O_(x)N_(y), Ta₂O₅, Nb₂O₅,AlN, Si₃N₄, AlO_(x)N_(y), SiO_(x)N_(y), SiN_(x), SiN_(x):H_(y), HfO₂,TiO₂, ZrO₂, Y₂O₃, Al₂O₃, MoO₃, and diamond-like carbon. In one or moreembodiments, the high RI layer 130B may have high hardness (e.g.,hardness of greater than 8 GPa), and the high RI materials listed abovemay comprise high hardness and/or scratch resistance. The oxygen contentof the materials for the high RI layer 130B may be minimized, especiallyin SiN_(x) or AlN_(x) materials. AlO_(x)N_(y) materials may beconsidered to be oxygen-doped AlN_(x) (i.e., they may have an AlN_(x)crystal structure (e.g., wurtzite) and need not have an AlON crystalstructure). Exemplary AlO_(x)N_(y) high RI materials may comprise fromabout 0 atom % to about 20 atom % oxygen, or from about 5 atom % toabout 15 atom % oxygen, and any ranges and sub-ranges between theforegoing values, while including 30 atom % to about 50 atom % nitrogen,and any ranges and sub-ranges between the foregoing values. ExemplarySi_(u)Al_(v)O_(x)N_(y) high RI materials may comprise from about 10 atom% to about 30 atom % or from about 15 atom % to about 25 atom % silicon,from about 20 atom % to about 40 atom % or from about 25 atom % to about35 atom % aluminum, from about 0 atom % to about 20 atom % or from about1 atom % to about 20 atom % oxygen, and from about 30 atom % to about 50atom % nitrogen. The foregoing materials may be hydrogenated up to about30% by weight. Where a material having a medium refractive index isdesired, some embodiments may utilize AlN and/or SiO_(x)N_(y). It shouldbe understood that a scratch-resistant layer 150 may comprise any of thematerials disclosed as suitable for use in a high RI layer.

As depicted in FIG. 2 , in one or more embodiments, the optical coating120 may comprise a scratch-resistant layer 150 that is integrated as ahigh RI layer, and one or more low RI layers 130A and high RI layers130B may be positioned over the scratch-resistant layer 150. Thescratch-resistant layer may be alternately defined as the thickest highRI layer in the overall optical coating 120 or in the overall coatedarticle 100. Without being bound by theory, it is believed that thecoated article 100 may exhibit increased hardness at indentation depthswhen a relatively thin amount of material is deposited over thescratch-resistant layer 150. Further, the inclusion of low RI and highRI layers over the scratch-resistant layer 150 may enhance the opticalproperties of the coated article 100. In some embodiments, relativelyfew layers (e.g., 1, 2, 3, 4, or 5 layers) may positioned over thescratch-resistant layer 150 and these layers may each be relatively thin(e.g. less than 100 nm, less than 75 nm, less than 50 nm, or even lessthan 25 nm, and any ranges and sub-ranges between the foregoing values).

The scratch-resistant layer 150 may be relatively thick as compared withother layers, such as greater than or equal to about 300 nm, 400 nm, 500nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 micron, 2 microns, 3 microns, 4microns, 5 microns, 6 microns, 7 microns, or even 8 microns, and anyranges and sub-ranges between the foregoing values. For example ascratch-resistant layer may have a thickness from about 300 nm to about10 microns.

In one or more embodiments, the optical coating 120 may include one ormore additional top coatings 140 disposed on the anti-reflective opticalcoating 120, as shown in FIG. 2 . In one or more embodiments, theadditional top coating 140 may include an easy-to-clean coating. Anexample of a suitable an easy-to-clean coating is described in U.S.patent application Ser. No. 13/690,904, entitled “PROCESS FOR MAKING OFGLASS ARTICLES WITH OPTICAL AND EASY-TO-CLEAN COATINGS,” filed on Nov.30, 2012, which is incorporated herein in its entirety by reference. Theeasy-to-clean coating may have a thickness in the range from about 1 nmto about 50 nm, and any ranges and sub-ranges between the foregoingvalues, and may include known materials such as fluorinated silanes. Theeasy-to-clean coating may alternately or additionally comprise alow-friction coating or surface treatment. Exemplary low-frictioncoating materials may include diamond-like carbon, silanes (e.g.fluorosilanes), phosphonates, alkenes, and alkynes. In some embodiments,the easy-to-clean coating may have a thickness in the range from about 1nm to about 40 nm, from about 1 nm to about 30 nm, from about 1 nm toabout 25 nm, from about 1 nm to about 20 nm, from about 1 nm to about 15nm, from about 1 nm to about 10 nm, from about 5 nm to about 50 nm, fromabout 10 nm to about 50 nm, from about 15 nm to about 50 nm, from about7 nm to about 20 nm, from about 7 nm to about 15 nm, from about 7 nm toabout 12 nm or from about 7 nm to about 10 nm, and all ranges andsub-ranges therebetween.

The top coating 140 may include a scratch-resistant layer or layerswhich comprise any of the materials disclosed as being suitable for usein the scratch-resistant coating 150. In some embodiments, theadditional coating 140 includes a combination of easy-to-clean materialand scratch-resistant material. In one example, the combination includesan easy-to-clean material and diamond-like carbon. Such additional topcoatings 140 may have a thickness in the range from about 1 nm to about50 nm. The constituents of the additional coating 140 may be provided inseparate layers. For example, the diamond-like carbon may be disposed asa first layer and the easy-to clean can be disposed as a second layer onthe first layer of diamond-like carbon. The thicknesses of the firstlayer and the second layer may be in the ranges provided above for theadditional coating. For example, the first layer of diamond-like carbonmay have a thickness of about 1 nm to about 20 nm or from about 4 nm toabout 15 nm (or more specifically about 10 nm), and any ranges andsub-ranges between the foregoing values, and the second layer ofeasy-to-clean may have a thickness of about 1 nm to about 10 nm (or morespecifically about 6 nm), and any ranges and sub-ranges between theforegoing values. The diamond-like coating may include tetrahedralamorphous carbon (Ta—C), Ta—C:H, and/or a-C—H.

In one or more embodiments, at least one of the layers (such as a low RIlayer 130A or a high RI layer 130B) of the anti-reflective coating 130may include a specific optical thickness (or optical thickness range).As used herein, the term “optical thickness” refers to the product ofthe physical thickness and the refractive index of a layer. In one ormore embodiments, at least one of the layers of the anti-reflectivecoating 130 may have an optical thickness in the range from about 2 nmto about 200 nm, from about 10 nm to about 100 nm, from about 15 nm toabout 100 nm, from about 15 to about 500 nm, or from about 15 to about5000 nm, and any ranges and sub-ranges between the foregoing values. Insome embodiments, all of the layers in the anti-reflective coating 130may each have an optical thickness in the range from about 2 nm to about200 nm, from about 10 nm to about 100 nm, from about 15 nm to about 100nm, from about 15 to about 500 nm, or from about 15 to about 5000 nm,and any ranges and sub-ranges between the foregoing values. In someembodiments, at least one layer of the anti-reflective coating 130 hasan optical thickness of about 50 nm or greater. In some embodiments,each of the low RI layers 103A have an optical thickness in the rangefrom about 2 nm to about 200 nm, from about 10 nm to about 100 nm, fromabout 15 nm to about 100 nm, from about 15 to about 500 nm, or fromabout 15 to about 5000 nm, and any ranges and sub-ranges between theforegoing values. In some embodiments, each of the high RI layers 130Bhave an optical thickness in the range from about 2 nm to about 200 nm,from about 10 nm to about 100 nm, from about 15 nm to about 100 nm, fromabout 15 to about 500 nm, or from about 15 to about 5000 nm, and anyranges and sub-ranges between the foregoing values. In embodiments witha three layer period, each of the medium RI layers have an opticalthickness in the range from about 2 nm to about 200 nm, from about 10 nmto about 100 nm, from about 15 nm to about 100 nm, from about 15 toabout 500 nm, or from about 15 to about 5000 nm, and any ranges andsub-ranges between the foregoing values.

In one or more embodiments, the optical coating may comprise one or moregradient layers, which each may comprise a compositional gradient alongtheir respective thicknesses, as shown in FIG. 3 . In some embodiments,the optical coating 120 may comprise a bottom gradient layer 170, ascratch-resistant layer 150 (as described above), and a top gradientlayer 160. FIG. 4 depicts an example refractive index profile of anoptical coating 120 of FIG. 3 . The substrate 110, bottom gradient layer170, scratch-resistant layer 150, and top gradient layer 160 are markedin their corresponding portions on the refractive index profile of FIG.4 . The bottom gradient layer 170 may be positioned in direct contactwith the substrate 110. The scratch-resistant layer 150 may be over thebottom gradient layer 170, and the top gradient layer may be in directcontact and over the scratch-resistant layer 150. The scratch-resistantlayer 150 may comprise one or more relatively hard materials with highrefractive indices, such as SiN_(x). In embodiments, the thickness ofthe scratch-resistant layer 150 may be from about 300 nm to severalmicrons, such as is described with reference to the scratch-resistantlayer 150 in other embodiments. The bottom gradient layer 170 may have arefractive index which varies from about the refractive index of thesubstrate (which may be relatively low) in portions which contact thesubstrate 110 to the refractive index of the scratch-resistant layer 150(which may be relatively high) in portions that contact thescratch-resistant layer 150. The bottom gradient layer 170 may have athickness of from about 10 nm to several microns, such as 50 nm to 1000nm, 100 nm to 1000 nm, or 500 nm to 1000 nm, and any ranges andsub-ranges between the foregoing values. The top gradient layer 160 mayhave a refractive index which varies from about the refractive index ofthe scratch-resistant layer 150 (which may be relatively high) atportions which contact the scratch-resistant layer 150 to a relativelylow refractive index at the air interface at the air-side surface 122.The uppermost portion of the top gradient layer 160 (at the air-sidesurface 122) may comprise materials with a refractive index of 1.38 to1.55, such as, but not limited to, silicate glass, silica, phosphorousglass, or magnesium fluoride.

In one or more embodiments, the refractive index of the bottom gradientlayer 170 at the substrate may be within 0.2 (such as within 0.15, 0.1,0.05, 0.02, or 0.01, and any ranges and sub-ranges between the foregoingvalues) of the refractive index of the substrate 110. The refractiveindex of the bottom gradient layer 170 at the scratch-resistant layer150 may be within 0.2 (such as within 0.15, 0.1, 0.05, 0.02, or 0.01,and any ranges and sub-ranges between the foregoing values) of therefractive index of the scratch-resistant layer 150. The refractiveindex of the top gradient layer 160 at the scratch-resistant layer 150may be within 0.2 (such as within 0.15, 0.1, 0.05, 0.02, or 0.01, andany ranges and sub-ranges between the foregoing values) of therefractive index of the scratch-resistant layer 150. The refractiveindex of the top gradient layer 160 at the air-side surface 122 may befrom about 1.38 to about 1.55. In embodiments, the refractive index ofthe scratch-resistant layer may be about 1.75 or more, for example 1.8,or even 1.9, or any ranges and sub-ranges between the foregoing values.

In one or more embodiments, a single layer or multiple layers of theoptical coating 120 may be deposited onto the substrate 110 by a vacuumdeposition technique such as, for example, chemical vapor deposition(“CVD”) (e.g., plasma enhanced CVD (PECVD), low-pressure CVD,atmospheric pressure CVD, and plasma-enhanced atmospheric pressure CVD),physical vapor deposition (“PVD”) (e.g., reactive or nonreactivesputtering or laser ablation), thermal or e-beam evaporation and/oratomic layer deposition. Liquid-based methods may also be used such asspraying, dipping, spin coating, or slot coating (e.g., using sol-gelmaterials). Generally, vapor deposition techniques may include a varietyof vacuum deposition methods which can be used to produce thin films.For example, physical vapor deposition uses a physical process (such asheating or sputtering) to produce a vapor of material, which is thendeposited on the object which is coated.

In one or more embodiments, optical coating 120, or one or more layersof the optical coating 120 may have introduced residual compressivestress by utilizing particular vacuum deposition process parameters.Parameters such as deposition pressure, material composition, depositiontemperature, bias of the substrate, and ion gun current are contemplatedas parameters that may affect residual compressive stress of thedeposited layer. It should be understood that various depositedmaterials may react differently to varying deposition processparameters, and that process parameters may be different for differentdeposited materials.

According to one or more embodiments, the pressure during deposition mayaffect the residual stress in the coating. In some embodiments, higherpressure may form greater tensile stress, and lower pressure duringdeposition may form residual compressive stress. In one or moreembodiments, the residual compressive stress and/or thestrain-to-failure may be increased when the pressure utilized duringdeposition is about 1% or more, for example 2%, 3%, 4%, 5%, 10%, 15%, oreven 20%, or any ranges or sub-ranges between the foregoing values, lessthan normally utilized to form coatings with relatively low residualstress.

In some embodiments, the material composition of the coating may affectthe residual stress of the coating. For example, AlN may typically havea tensile stress that is not suitable in some embodiments describedherein. However, Al₂O₃ may generally have a residual compressive stresssuitable for embodiments. AlON may be tuned for residual compressivestress based on the stoichiometric ratio of N to O.

In additional embodiments, the bias of the substrate during depositionmay affect residual stress. For example, a negative DC bias on thesubstrate may promote the formation of a coating having residualcompressive stress, and a positive DC bias on the substrate may promotethe formation of tensile stress in the coating. Additionally, an RF biasmay promote the formation of a coating with residual compressive stress.

In additional embodiments, deposition at high temperatures may promotethe formation of residual compressive stress based the difference in CTEof the substrate and the coating. For example, when the substrate andcoating are cooled following deposition at increased temperatures, theyform residual stress depending upon the amount of cooling and the degreeof CTE mismatch between the substrate and the coating.

In additional embodiments, the rate of deposition may affect theresidual stress. For example, particular materials may form residualcompressive stress when deposited at certain rates, and may havedifferent residual stress when deposited at another rate.

In additional embodiments, the use of an ion gun may form residualcompressive stress in the coating. Additionally, the current of autilized ion gun may affect the residual stress. For example, higher iongun current may form increased compressive residual stress in thecoating.

In one or more embodiments, the residual compressive stress may beintroduced to the optical coating by utilizing an ion-exchange process.Following deposition of the optical coating, the optical coating may becontacted by an ion-exchange bath, such as a hot salt bath. Sometimesion-exchange may be referred to as chemical strengthening. In anion-exchange process, smaller ions in the optical coating are replacedfor larger ions in the surface of the optical coating. In one or moreembodiments, the ions in the surface layer of the optical coating arereplaced by—or exchanged with—larger ions having the same valence oroxidation state. Ion exchange processes are typically carried out byimmersing the coated article 100 in a molten salt bath containing thelarger ions to be exchanged with the smaller ions in the substrate. Itwill be appreciated by those skilled in the art that parameters for theion exchange process, including, but not limited to, bath compositionand temperature, immersion time, the number of immersions of thesubstrate in a salt bath (or baths), use of multiple salt baths,additional steps such as annealing, washing, and the like, are generallydetermined by the composition of the optical coating 120 and the desiredresidual compressive stress (CS), depth of residual compressive stresslayer (or depth of layer) of the optical coating 120 that result fromthe strengthening operation. By way of example, ion exchange of alkalimetal-containing optical coatings 120 may be achieved by immersion in atleast one molten bath containing a salt such as, but not limited to,nitrates, sulfates, and chlorides of the larger alkali metal ion. Thetemperature of the molten salt bath typically is in a range from about100° C. to about 1000° C., such as from about 380° C. up to about 450°C., and any ranges and sub-ranges between the foregoing values, whileimmersion times range from about 15 minutes up to about 40 hours, andany ranges and sub-ranges between the foregoing values. However,temperatures and immersion times different from those described abovemay also be used. It should be understood that the substrate 110 may beion-exchanged in a separate step, or may be ion-exchanged in the sameprocess step where the optical coating 120 is ion-exchanged.

According to some embodiments, the optical coating 120 may beion-exchanged by exposing deposited films to a field-assistedion-exchange process to achieve a larger-ion-for-smaller-ion exchangereaction within the structure of the optical coating 120. Likeion-exchange by contact with a molten salt bath, field-assistedion-exchange processes may induce a residual compressive stress in theoptical coating 120. Field-assisted ion-exchange processes includeapplying an electric field to the substrate with which ion-exchange istaking place to assist in the ion-exchange process. Examples offield-assisted ion-exchange processes are described in US PublishedPatent Application 2015/0166407 to Saxon Glass Technologies, Inc.

In one or more embodiments, the residual compressive stress may beintroduced to the optical coating 120 by utilizing an ion-implantationprocess. Ion-implantation processing refers to a method whereby ions ofa material are accelerated in an electrical field and impacted into asolid, such as the optical coating 120. The ions alter the elementalcomposition of the optical coating 120 (if the ions differ incomposition from the optical coating 120), by stopping in the opticalcoating and staying there. The ions that impact the target also causechemical and physical changes in the target by transferring their energyand momentum to the electrons and atomic nuclei of the material of theoptical coating 120.

In one or more embodiments, the residual compressive stress may beintroduced to the optical coating 120 by utilizing a mechanical blastingprocess. In some embodiments, the mechanical blasting process comprisesbead-blasting or grit blasting process. However, other mechanicalblasting processes are contemplated herein such as wet abrasiveblasting, wheel blasting, hydro blasting, micro-abrasive blasting, andbristle blasting. According to one or more embodiments, the beadblasting process may create compression in the surface without creatingcracks or flaws that are greater than about 100 nm in size.

In one or more embodiments, the residual compressive stress may beintroduced to the optical coating 120 by depositing the optical coatingonto a deformed substrate under physical stress and then allowing thedeformed substrate to remove stress by reshaping itself (and thusintroducing stress into the optical coating). A substrate 110 could bedeformed by a physical force prior to and during the deposition of theoptical coating 120. For example, a glass sheet may be deformed bybending the glass sheet. Then, the optical coating is deposited onto thedeformed substrate 110, e.g., the bent glass sheet. Following depositionof the optical coating 120, the substrate 110 is permitted to return toits original pre-deformation shape (e.g., flat), thus introducing stressinto the optical coating 120. In embodiments, the substrate may be bentto a convex or concave shape relative to the deposition surface of thesubstrate 110, whereby the optical coating 120 is deposited onto theconvex or concave surface. When the convex or concave shape of thesubstrate 110 is removed (i.e., the substrate 110 returns to being aflat sheet), stresses are introduced into the optical coating 120.

In one or more embodiments, the residual compressive stress may beintroduced to the optical coating by increasing the difference in CTEbetween the optical coating and the substrate, or increasing the coatingdeposition process temperature, so that residual compressive stress isincreased as the coated article is cooled to room temperature. In someembodiments, the CTE of the optical coating 120 may be less that the CTEof the substrate 110. For example, in one or more embodiments, the ratioof the CTE of the substrate 110 to the CTE of at least a portion of theoptical coating is about 1.2 or more, for example, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, 1.9, 2, 3, 4, or even about 5 or more, and any ranges andsub-ranges between the foregoing values. In one or more embodiments, theoptical coating 120 may be deposited onto the substrate 110 at anelevated temperature (i.e., above room temperature). As the coatedarticle 100 is cooled to room temperature, residual compressive stressesmay be imparted on the optical coating 120. The CTE mismatch of theoptical coating 120 and the substrate 110 may cause the formation of theresidual compressive stress in the optical coating 120. In someembodiments, a portion of the optical coating 120 (such as one or morelayers) may have the relatively low CTE and therefore, the residualcompressive stress may be imparted on a portion of the optical coating120. Portions of the optical coating 120 with a relatively greater CTEmismatch relative to the substrate 110 may have higher levels ofresidual compressive stress.

More than one technique disclosed herein may be utilized to achieve highresidual compressive stress and/or strain-to-failure in the opticalcoating. For example, one or more of utilizing particular depositionparameters (e.g., pressure, rate, ion-assist), utilizing an ion-exchangeprocess, utilizing an ion-implantation process, utilizing a mechanicalblasting process, depositing the optical coating onto a deformedsubstrate under physical stress and then allowing the deformed substrateto remove stress by reshaping itself (and thus introducing stress intothe optical coating), or increasing the difference in CTE between theoptical coating and the substrate so that residual compressive stress isincreased as the coated article is cooled to room temperature (from anelevated temperature) may be utilized in combination.

The substrate 110 may include an inorganic material and may include anamorphous substrate, a crystalline substrate or a combination thereof.The substrate 110 may be formed from man-made materials and/or naturallyoccurring materials (e.g., quartz and polymers). For example, in someinstances, the substrate 110 may be characterized as organic and mayspecifically be polymeric. Examples of suitable polymers include,without limitation: thermoplastics including polystyrene (PS) (includingstyrene copolymers and blends), polycarbonate (PC) (including copolymersand blends), polyesters (including copolymers and blends, includingpolyethyleneterephthalate and polyethyleneterephthalate copolymers),polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride(PVC), acrylic polymers including polymethyl methacrylate (PMMA)(including copolymers and blends), thermoplastic urethanes (TPU),polyetherimide (PEI) and blends of these polymers with each other. Otherexemplary polymers include epoxy, styrenic, phenolic, melamine, andsilicone resins.

In some specific embodiments, the substrate 110 may specifically excludepolymeric, plastic and/or metal substrates. The substrate 110 may becharacterized as alkali-including substrates (i.e., the substrateincludes one or more alkalis). In one or more embodiments, the substrateexhibits a refractive index in the range from about 1.45 to about 1.55.In specific embodiments, the substrate 110 may exhibit an averagestrain-to-failure at a surface on one or more opposing major surfacethat is 0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% orgreater, 0.9% or greater, 1% or greater, 1.1% or greater, 1.2% orgreater, 1.3% or greater, 1.4% or greater 1.5% or greater or even 2% orgreater, and any ranges and sub-ranges between the foregoing values, asmeasured using Ring-on-Ring Tensile Testing, using 5 samples andaveraging the values from those 5 samples. A synchronized video camerawas used to capture crack onset strain levels as well as catastrophicglass failure levels. In specific embodiments, the substrate 110 mayexhibit an average strain-to-failure at its surface on one or moreopposing major surface of about 1.2%, about 1.4%, about 1.6%, about1.8%, about 2.2%, about 2.4%, about 2.6%, about 2.8%, or about 3% orgreater, and any ranges and sub-ranges between the foregoing values.

Suitable substrates 110 may exhibit an elastic modulus (or Young'smodulus) in the range from about 30 GPa to about 120 GPa, and any rangesand sub-ranges between the foregoing values. In some instances, theelastic modulus of the substrate may be in the range from about 30 GPato about 110 GPa, from about 30 GPa to about 100 GPa, from about 30 GPato about 90 GPa, from about 30 GPa to about 80 GPa, from about 30 GPa toabout 70 GPa, from about 40 GPa to about 120 GPa, from about 50 GPa toabout 120 GPa, from about 60 GPa to about 120 GPa, from about 70 GPa toabout 120 GPa, and all ranges and sub-ranges therebetween.

In one or more embodiments, an amorphous substrate may include glass,which may be strengthened or non-strengthened. Examples of suitableglass include soda lime glass, alkali aluminosilicate glass, alkalicontaining borosilicate glass and alkali aluminoborosilicate glass. Insome variants, the glass may be free of lithia. In one or morealternative embodiments, the substrate 110 may include crystallinesubstrates such as glass-ceramic substrates (which may be strengthenedor non-strengthened) or may include a single crystal structure, such assapphire. In one or more specific embodiments, the substrate 110includes an amorphous base (e.g., glass) and a crystalline cladding(e.g., sapphire layer, a polycrystalline alumina layer and/or or aspinel (MgAl₂O₄) layer).

The substrate 110 of one or more embodiments may have a hardness that isless than the hardness of the article (as measured by the BerkovichIndenter Hardness Test described herein).

The substrate 110 may be transparent or substantially optically clear,i.e., the substrate 110 may exhibit an average light transmission overthe optical wavelength regime of about 85% or greater, about 86% orgreater, about 87% or greater, about 88% or greater, about 89% orgreater, about 90% or greater, about 91% or greater or about 92% orgreater, and any ranges and sub-ranges between the foregoing values. Inone or more alternative embodiments, the substrate 110 may be opaque orexhibit an average light transmission over the optical wavelength regimeof less than about 10%, less than about 9%, less than about 8%, lessthan about 7%, less than about 6%, less than about 5%, less than about4%, less than about 3%, less than about 2%, less than about 1%, or lessthan about 0.5%, and any ranges and sub-ranges between the foregoingvalues. In some embodiments, these light transmittance values may be atotal transmittance (taking into account transmittance of light throughboth major surfaces of the substrate). In some embodiments, these lightreflectance values may be a total reflectance (taking into accountreflectance from both major surfaces of the substrate) or may beobserved on a single side of the substrate (i.e., on the air-sidesurface 122 only, without taking into account the opposite surface).Unless otherwise specified, the average reflectance or transmittance ofthe substrate alone, or the article when coated, are specified usingtransmittance through both major surfaces of the substrate, and usingreflectance from only the coating and coated side of the substrate.Also, unless otherwise specified, the average reflectance ortransmittance of the substrate alone, or of the article when coated, ismeasured at an incident illumination angle of 0 degrees relative to thesubstrate surface 112 (however, such measurements may be provided atincident illumination angles of 45 degrees or 60 degrees). The substrate110 may optionally exhibit a color, such as white, black, red, blue,green, yellow, orange etc.

Additionally or alternatively, the physical thickness of the substrate110 may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the substrate 110 may bethicker as compared to more central regions of the substrate 110. Thelength, width and physical thickness dimensions of the substrate 110 mayalso vary according to the application or use of the article 100.

The substrate 110 may be provided using a variety of differentprocesses. For instance, where the substrate 110 includes an amorphoussubstrate such as glass, various forming methods can include float glassprocesses and down-draw processes such as fusion draw and slot draw,up-draw, and press rolling.

Once formed, a substrate 110 may be strengthened to form a strengthenedsubstrate. As used herein, the term “strengthened substrate” may referto a substrate that has been chemically strengthened, for examplethrough ion-exchange of larger ions for smaller ions in the surface ofthe substrate. However, other strengthening methods known in the art,such as thermal tempering, or utilizing a mismatch of the CTE betweenportions of the substrate to create compressive stress and centraltension regions, may be utilized to form strengthened substrates.

Where the substrate 110 is chemically strengthened by an ion exchangeprocess, the ions in the surface layer of the substrate are replacedby—or exchanged with—larger ions having the same valence or oxidationstate. Ion exchange processes are typically carried out by immersing asubstrate in a molten salt bath containing the larger ions to beexchanged with the smaller ions in the substrate. It will be appreciatedby those skilled in the art that parameters for the ion exchangeprocess, including, but not limited to, bath composition andtemperature, immersion time, the number of immersions of the substratein a salt bath (or baths), use of multiple salt baths, additional stepssuch as annealing, washing, and the like, are generally determined bythe composition of the substrate and the desired compressive stress(CS), depth of compressive stress layer (or depth of compression, DOC)of the substrate that result from the strengthening operation. By way ofexample, ion exchange of alkali metal-containing glass substrates may beachieved by immersion in at least one molten bath containing a salt suchas, but not limited to, nitrates, sulfates, and chlorides of the largeralkali metal ion. The temperature of the molten salt bath typically isin a range from about 380° C. up to about 450° C., and any ranges andsub-ranges between the foregoing values, while immersion times rangefrom about 15 minutes up to about 40 hours, and any ranges andsub-ranges between the foregoing values. However, temperatures andimmersion times different from those described above may also be used.

In addition, non-limiting examples of ion exchange processes in whichglass substrates are immersed in multiple ion exchange baths, withwashing and/or annealing steps between immersions, are described in U.S.patent application Ser. No. 12/500,650, filed Jul. 10, 2009, by DouglasC. Allan et al., entitled “Glass with Compressive Surface for ConsumerApplications” and claiming priority from U.S. Provisional PatentApplication No. 61/079,995, filed Jul. 11, 2008, in which glasssubstrates are strengthened by immersion in multiple, successive, ionexchange treatments in salt baths of different concentrations; and U.S.Pat. No. 8,312,739, by Christopher M. Lee et al., issued on Nov. 20,2012, and entitled “Dual Stage Ion Exchange for Chemical Strengtheningof Glass,” and claiming priority from U.S. Provisional PatentApplication No. 61/084,398, filed Jul. 29, 2008, in which glasssubstrates are strengthened by ion exchange in a first bath is dilutedwith an effluent ion, followed by immersion in a second bath having asmaller concentration of the effluent ion than the first bath. Thecontents of U.S. patent application Ser. No. 12/500,650 and U.S. Pat.No. 8,312,739 are incorporated herein by reference in their entirety.

The degree of chemical strengthening achieved by ion exchange may bequantified based on the parameters of central tension (CT), surface CS,and depth of compression (DOC). Surface CS may be measured near thesurface or within the strengthened glass at various depths. A maximum CSvalue may include the measured CS at the surface (CS_(s)) of thestrengthened substrate. Maximum CT values are measured using a scatteredlight polariscope (SCALP) technique known in the art.

Compressive stress (at the surface of the glass) is measured by surfacestress meter (FSM) using commercially available instruments such as theFSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surfacestress measurements rely upon the accurate measurement of the stressoptical coefficient (SOC), which is related to the birefringence of theglass. SOC in turn is measured according to Procedure C (Glass DiscMethod) described in ASTM standard C770-16, entitled “Standard TestMethod for Measurement of Glass Stress-Optical Coefficient,” thecontents of which are incorporated herein by reference in theirentirety.

As used herein, depth of compression (DOC) means the depth at which thestress in the chemically strengthened alkali aluminosilicate glassarticle described herein changes from compressive to tensile. DOC may bemeasured by FSM or by SCALP depending on the ion exchange treatment.Where the stress in the glass article is generated by exchangingpotassium ions into the glass article, FSM is used to measure DOC. Wherethe stress is generated by exchanging sodium ions into the glassarticle, SCALP is used to measure DOC. Where the stress in the glassarticle is generated by exchanging both potassium and sodium ions intothe glass, the DOC is measured by SCALP, since it is believed theexchange depth of sodium indicates the DOC and the exchange depth ofpotassium ions indicates a change in the magnitude of the compressivestress (but not the change in stress from compressive to tensile); theexchange depth of potassium ions in such glass articles is measured byFSM.

In some embodiments, a strengthened substrate 110 can have a surface CSof 250 MPa or greater, 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater, and any ranges and sub-ranges between the foregoingvalues. The strengthened substrate may have a DOC of 10 μm or greater,15 μm or greater, 20 μm or greater (e.g., 25 μm, 30 μm, 35 μm, 40 μm, 45μm, 50 μm or greater), and any ranges and sub-ranges between theforegoing values, and/or a CT of 10 MPa or greater, 20 MPa or greater,30 MPa or greater, 40 MPa or greater (e.g., 42 MPa, 45 MPa, or 50 MPa orgreater), and any ranges and sub-ranges between the foregoing values,but less than 100 MPa (e.g., 95, 90, 85, 80, 75, 70, 65, 60, 55 MPa orless), and any ranges and sub-ranges between the foregoing values. Inone or more specific embodiments, the strengthened substrate has one ormore of the following: a surface CS greater than 500 MPa, a DOC greaterthan 15 μm, and a CT greater than 18 MPa.

Example glasses that may be used in the substrate 110 may include alkalialuminosilicate glass compositions or alkali aluminoborosilicate glasscompositions, though other glass compositions are contemplated. Suchglass compositions are capable of being chemically strengthened by anion exchange process. One example glass composition comprises SiO₂, B₂O₃and Na₂O, where (SiO₂+B₂O₃)>66 mol. %, and Na₂O>9 mol. %. In someembodiments, the glass composition includes 6 wt. % or more aluminumoxide. In further embodiments, the substrate 110 includes a glasscomposition with one or more alkaline earth oxides, such that a contentof alkaline earth oxides is 5 wt. % or more. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In some embodiments, the glass compositions used in thesubstrate can comprise 61-75 mol. % SiO₂; 7-15 mol. % Al₂O₃; 0-12 mol. %B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3 mol. %CaO.

A further example glass composition suitable for the substratecomprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol. %(Li₂O+Na₂O+K₂O) 20 mol. % and 0 mol. % (MgO+CaO) 10 mol. %.

A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.% (Li₂O+Na₂O+K₂O) 18 mol. % and 2 mol. % (MgO+CaO) 7 mol. %.

In some embodiments, an alkali aluminosilicate glass compositionsuitable for the substrate 110 comprises alumina, at least one alkalimetal and, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments 58 mol. % SiO₂ or more, and in still other embodiments 60mol. % SiO₂ or more, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e.,sum of modifiers) is greater than 1, where in the ratio the componentsare expressed in mol. % and the modifiers are alkali metal oxides. Thisglass composition, in particular embodiments, comprises: 58-72 mol. %SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol. % B₂O₃; 8-16 mol. % Na₂O; and 0-4mol. % K₂O, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e., sum ofmodifiers) is greater than 1.

In some embodiments, the substrate may include an alkali aluminosilicateglass composition comprising: 64-68 mol. % SiO₂; 12-16 mol. % Na₂O; 8-12mol. % Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. % MgO; and 0-5mol. % CaO, wherein: 66 mol. %≤SiO₂+B₂O₃+CaO≤69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)−Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O—Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)−Al₂O₃≤10 mol. %.

In some embodiments, the substrate 110 may comprise an alkalialuminosilicate glass composition comprising: 2 mol % or more of Al₂O₃and/or ZrO₂, or 4 mol % or more of Al₂O₃ and/or ZrO₂.

Where the substrate 110 includes a crystalline substrate, the substratemay include a single crystal, which may include Al₂O₃. Such singlecrystal substrates are referred to as sapphire. Other suitable materialsfor a crystalline substrate include polycrystalline alumina layer and/orspinel (MgAl₂O₄).

Optionally, the substrate 110 may include a glass-ceramic substrate,which may be strengthened or non-strengthened. Glass-ceramics” includematerials produced through controlled crystallization of glass. Inembodiments, glass-ceramics have about 30% to about 90% crystallinity.Examples of suitable glass-ceramics may include Li₂O—Al₂O₃—SiO₂ system(i.e. LAS-System) glass-ceramics, MgO—Al₂O₃—SiO₂ system (i.e.MAS-System) glass-ceramics, and/or glass-ceramics that include apredominant crystal phase including β-quartz solid solution,β-spodumene, cordierite, and lithium disilicate. The glass-ceramicsubstrates may be strengthened using the chemical strengtheningprocesses disclosed herein. In one or more embodiments, MAS-Systemglass-ceramic substrates may be strengthened in Li₂SO₄ molten salt,whereby an exchange of 2Li⁺ for Mg²⁺ can occur.

The substrate 110 according to one or more embodiments can have aphysical thickness ranging from about 100 μm to about 5 mm, and anyranges and sub-ranges between the foregoing values, in various portionsof the substrate 110. In some embodiments, the substrate 110 physicalthicknesses ranges from about 100 μm to about 500 μm (e.g., 100, 200,300, 400 or 500 μm). In some embodiments, the substrate 110 physicalthicknesses ranges from about 500 μm to about 1000 μm (e.g., 500, 600,700, 800, 900 or 1000 μm), and any ranges and sub-ranges between theforegoing values. In some embodiments, substrate 110 may have a physicalthickness greater than about 1 mm (e.g., about 2, 3, 4, or 5 mm). Thesubstrate 110 may be acid polished or otherwise treated to remove orreduce the effect of surface flaws.

According to one or more embodiments described herein, a coated article100, an optical coating 120, or an individual layer of an opticalcoating 100 may have a strain-to-failure (i.e., a crack onset strain) ofgreater than or equal to about 0.4%, greater than or equal to about0.5%, greater than or equal to about 0.6%, greater than or equal toabout 0.7%, greater than or equal to about 0.8%, greater than or equalto about 0.9%, greater than or equal to about 1.0%, greater than orequal to about 1.5%, or even greater than or equal to about 2.0%, andany ranges and sub-ranges between the foregoing values. The term“strain-to-failure” refers to the strain at which cracks propagate inthe optical coating 120, substrate 110, or both simultaneously withoutapplication of additional load, typically leading to catastrophicfailure in a given material, layer or film and, perhaps even bridge toanother material, layer, or film, as defined herein. That is, breakageof the optical coating 120 without breakage of the substrate constitutesfailure, and breakage of the substrate 110 also constitutes failure. Theterm “average” when used in connection with average strain-to-failure orany other property is based on the mathematical average of measurementsof such property on 5 samples. Typically, crack onset strainmeasurements are repeatable under normal laboratory conditions, and thestandard deviation of crack onset strain measured in multiple samplesmay be as little as 0.01% of observed strain. Average strain-to-failureas used herein was measured using Ring-on-Ring Tensile Testing. However,unless stated otherwise, strain-to-failure measurements described hereinrefer to measurements from the ring-on-ring testing device describedherein below.

FIG. 5 schematically depicts a cross-sectional view of a ring-on-ringmechanical testing device 300 utilized to measure the strain-to-failurefor a coated article 100. According to the Ring-on-Ring Tensile TestingProcedure, the coated article 100 is positioned between the bottom ring302 and the top ring 304. The top ring 304 and the bottom ring 302 havedifferent diameters, where the diameter of the top ring 304 isrepresented by dashed line 308 and the diameter of the bottom ring 302is represented by dashed line 306. As used herein, the top ring 304 hasa diameter 308 of 12.7 mm and the bottom ring 302 has a diameter 306 of25.4 mm. The portion of the top ring 304 and bottom ring 302 whichcontact the coated article 100 are circular in cross section and eachhave radius of 1.6 mm. The top ring 304 and bottom ring 302 are made ofsteel. Testing is performed in an environment of about 22° C. with45%-55% relative humidity. The coated articles used for testing are 50mm by 50 mm squares in size.

To determine the strain-to-failure of the coated article 100, force isapplied to the top ring 304 in a downward direction and/or to the bottomring in an upward direction as orientation is shown in FIG. 5 . Theforce on the top ring 304 and or bottom ring 302 is increased, causingstrain in the coated article 100 until catastrophic failure of one orboth of the substrate 110 and the optical coating 120. A light andcamera (not depicted in FIG. 5 ) is provided below the bottom ring 30 torecord the catastrophic failure during testing. An electroniccontroller, such as a Dewetron acquisition system, is provided tocoordinate the camera images with the applied load to determine the loadwhen catastrophic damage is observed by the camera. FIG. 6 depicts animage of example failure in a Ring-on-Ring Tensile Testing Procedure. Todetermine the strain-to-failure, camera images and load signals aresynchronized through the Dewetron system, so that the load at which thecoating shows failure can be determined. Then, the finite elementanalysis, as found in “Hu, G., et al., Dynamic fracturing ofstrengthened glass under biaxial tensile loading. Journal ofNon-Crystalline Solids, 2014. 405(0): p. 153-158.)”, is used to analyzethe strain levels the sample is experiencing at this load. The elementsize may be chosen to be fine enough to be representative of the stressconcentration underneath the loading ring. The strain level is averagedover 30 nodal points or more underneath the loading ring.

The optical coating 120 and/or the article 100 may be described in termsof a hardness and/or Young's modulus measured by a Berkovich IndenterHardness Test. As used herein, the “Berkovich Indenter Hardness Test”includes measuring the Young's modulus of the thin film elements on aproxy layer. The proxy layer was made of the same material and wasdeposited by the same process used to generate the coating, but wasdeposited 300 nm thick onto a Gorilla® Glass substrate. Hardness andYoung's modulus of thin film coatings are determined using widelyaccepted nano-indentation practices. See: Fischer-Cripps, A. C.,Critical Review of Analysis and Interpretation of Nanoindentation TestData, Surface & Coatings Technology, 200, 4153-4165 (2006) (hereinafter“Fischer-Cripps”); and Hay, J., Agee, P, and Herbert, E., ContinuousStiffness measurement During Instrumented Indentation Testing,Experimental Techniques, 34 (3) 86-94 (2010) (hereinafter “Hay”). Forcoatings, it is typical to measure hardness and modulus as a function ofindentation depth. So long as the coating is of sufficient thickness, itis then possible to isolate the properties of the coating from theresulting response profiles. It should be recognized that if thecoatings are too thin (for example, less than ˜500 nm), it may not bepossible to completely isolate the coating properties as they can beinfluenced from the proximity of the substrate which may have differentmechanical properties. See Hay. The methods used to report theproperties herein are representative of the coatings themselves. Theprocess is to measure hardness and modulus versus indentation depth outto depths approaching 1000 nm. In the case of hard coatings on a softerglass, the response curves will reveal maximum levels of hardness andmodulus at relatively small indentation depths (</=about 200 nm). Atdeeper indentation depths both hardness and modulus will gradualdiminish as the response is influenced by the softer glass substrate. Inthis case the coating hardness and modulus are taken be those associatedwith the regions exhibiting the maximum hardness and modulus. In thecase of soft coatings on a harder glass substrate, the coatingproperties will be indicated by lowest hardness and modulus levels thatoccur at relatively small indentation depths. At deeper indentationdepths, the hardness and modulus will gradually increase due to theinfluence of the harder glass. These profiles of hardness and modulusversus depth can be obtained using either the traditional Oliver andPharr approach (as described in Fischer-Cripps) or by the more efficientcontinuous stiffness approach (see Hay). Extraction of reliablenano-indentation data requires that well-established protocols befollowed. Otherwise, these metrics can be subject to significant errors.These elastic modulus and hardness values are measured for such thinfilms using known diamond nano-indentation methods, as described above,with a Berkovich diamond indenter tip.

Typically, in nano-indentation measurement methods (such as by using aBerkovich indenter) where the coating is harder than the underlyingsubstrate, the measured hardness may appear to increase initially due todevelopment of the plastic zone at shallow indentation depths (e.g.,less than 25 nm or less than 50 nm) and then increases and reaches amaximum value or plateau at deeper indentation depths (e.g., from 50 nmto about 500 nm or 1000 nm). Thereafter, hardness begins to decrease ateven deeper indentation depths due to the effect of the underlyingsubstrate when the substrate is softer than the coating. Where asubstrate having a greater hardness compared to the coating is utilized,the same effect can be seen; however, the hardness increases at deeperindentation depths due to the effect of the underlying substrate.

The indentation depth range and the hardness values at certainindentation depth ranges can be selected to identify a particularhardness response of the optical coatings 120 and layers thereof,described herein, without the effect of the underlying substrate 110.When measuring hardness of the optical coating 120 (when disposed on asubstrate 110) with a Berkovich indenter, the region of permanentdeformation (plastic zone) of a material is associated with the hardnessof the material. During indentation, an elastic stress field extendswell beyond this region of permanent deformation. As indentation depthincreases, the apparent hardness and modulus are influenced by stressfield interactions with the underlying substrate 110. The influence ofthe substrate on hardness occurs at deeper indentation depths (i.e.,typically at depths greater than about 10% of the optical coating 120).Moreover, a further complication is that the hardness response isdeveloped by a certain minimum load to develop full plasticity duringthe indentation process. Prior to that certain minimum load, thehardness shows a generally increasing trend.

At small indentation depths (which also may be characterized as smallloads) (e.g., up to about 50 nm), the apparent hardness of a materialappears to increase dramatically versus indentation depth. This smallindentation depth regime does not represent a true metric of hardnessbut, instead, reflects the development of the aforementioned plasticzone, which is related to the finite radius of curvature of theindenter. At intermediate indentation depths, the apparent hardnessapproaches maximum levels. At deeper indentation depths, the influenceof the substrate becomes more pronounced as the indentation depthsincrease. Hardness may begin to drop dramatically once the indentationdepth exceeds about 30% of the optical coating thickness.

In one or more embodiments, the coated article 100 may exhibit ahardness of about 5 GPa or greater, about 8 GPa or greater, about 10 GPaor greater or about 12 GPa or greater (e.g., 14 GPa or greater, 16 GPaor greater, 18 GPa or greater, or even 20 GPa or greater), and anyranges and sub-ranges between the foregoing values, as measured on theair-side surface 122, by a Berkovich Indenter Hardness Test. In one ormore embodiments, the optical coating 120 may exhibit a maximum hardnessof about 8 GPa or greater, about 10 GPa or greater, or about 12 GPa orgreater (e.g., 14 GPa or greater, 16 GPa or greater, 18 GPa or greater,or even 20 GPa or greater), and any ranges and sub-ranges between theforegoing values as measured on the air-side surface 122 by a BerkovichIndenter Hardness Test. In some embodiments, the maximum hardness of thehigh RI layer and/or the scratch-resistant layer 150, as measured by theBerkovich Indenter Hardness Test, may be about 8 GPa or greater, about10 GPa or greater, about 12 GPa or greater, about 15 GPa or greater,about 18 GPa or greater, or even about 20 GPa or greater, and any rangesand sub-ranges between the foregoing values. Measurement of a singlelayer can be conducted by applying the single layer to the article andtesting for maximum Berkovich hardness. Such measured hardness valuesmay be exhibited by the coated article 100, optical coating 120, high RIlayer 130B, and/or scratch-resistant layer 150 along an indentationdepth of about 50 nm or greater or about 100 nm or greater (e.g., fromabout 100 nm to about 300 nm, from about 100 nm to about 400 nm, fromabout 100 nm to about 500 nm, from about 100 nm to about 600 nm, fromabout 200 nm to about 300 nm, from about 200 nm to about 400 nm, fromabout 200 nm to about 500 nm, or from about 200 nm to about 600 nm), andany ranges and sub-ranges between the foregoing values. In one or moreembodiments, the article exhibits a hardness that is greater than thehardness of the substrate (which can be measured on the opposite surfacefrom the air-side surface 122).

Optical interference between reflected waves from the optical coating120/air interface and the optical coating 120/substrate 110 interfacecan lead to spectral reflectance and/or transmittance oscillations thatcreate apparent color in the article 100. As used herein, the term“transmittance” is defined as the percentage of incident optical powerwithin a given wavelength range transmitted through a material (e.g.,the article, the substrate or the optical film or portions thereof). Theterm “reflectance” is similarly defined as the percentage of incidentoptical power within a given wavelength range that is reflected from amaterial (e.g., the article, the substrate, or the optical film orportions thereof). As used herein, an “average transmission” refers tothe average amount of incident optical power transmitted through amaterial over a defined optical wavelength regime. As used herein, an“average reflectance” refers to the average amount of incident opticalpower reflected by the material. Reflectance may be measured as a singleside reflectance when measured at the air-side surface 122 only (e.g.,when removing the reflections from an uncoated back surface (e.g., 114in FIG. 1 ) of the coated article 100, such as through usingindex-matching oils on the back surface coupled to an absorber, or otherknown methods). In one or more embodiments, the spectral resolution ofthe characterization of the transmittance and reflectance is less than 5nm or 0.02 eV. The color may be more pronounced in reflection. Theangular color may shift in reflection with viewing angle due to a shiftin the spectral reflectance oscillations with incident illuminationangle. Angular color shifts in transmittance with viewing angle are alsodue to the same shift in the spectral transmittance oscillation withincident illumination angle. The observed color and angular color shiftswith incident illumination angle are often distracting or objectionableto device users, particularly under illumination with sharp spectralfeatures such as fluorescent lighting and some LED lighting. Angularcolor shifts in transmission may also play a factor in color shift inreflection and vice versa. Factors in angular color shifts intransmission and/or reflection may also include angular color shifts dueto viewing angle or angular color shifts away from a certain white pointthat may be caused by material absorption (somewhat independent ofangle) defined by a particular illuminant or test system.

The articles described herein exhibit an average light transmission anda single side average light reflectance over a specified wavelengthranges in or near the visible spectrum. Additionally, the articlesdescribed herein exhibit an average visible photopic transmittance andan average visible photopic reflectance over a specified wavelengthrange in the visible spectrum. In embodiments, the wavelength ranges(sometimes referred to herein as an “optical wavelength regime”) formeasuring average light transmission, single side average lightreflectance, average visible photopic transmission, and average visiblephotopic reflectance are from about 450 nm to about 650 nm, from about420 nm to about 680 nm, from about 420 nm to about 700 nm, from about420 nm to about 740 nm, from about 420 nm to about 850 nm, from about420 nm to about 950 nm, or preferably from about 350 nm to about 850 nm.Unless otherwise specified, the average light transmission, single sideaverage light reflectance, average visible photopic transmission, andaverage visible photopic reflectance are measured at an incidentillumination angle near normal to the anti-reflective surface 122, suchas at an angle of incidence of from about 0 degrees to about 10 degrees(however, such measurements may be collected at other incidentillumination angles, such as, e.g., 30 degrees, 45 degrees, or 60degrees).

In one or more embodiments, a coated article 100 may exhibit an averagesingle side light reflectance of about 50% or less, 40% or less, 30% orless, 20% or less, 10% or less, 9% or less, about 8% or less, about 7%or less, about 6% or less, about 5% or less, about 4% or less, about 3%or less, or even about 2% or less, and any ranges and sub-ranges betweenthe foregoing values, over the optical wavelength regime, when measuredat the air-side surface 122 only (e.g., when removing the reflectionsfrom an uncoated back surface of the article, such as through usingindex-matching oils on the back surface coupled to an absorber). In someembodiments, the average single side light reflectance may be in therange from about 0.4% to about 9%, from about 0.4% to about 8%, fromabout 0.4% to about 7%, from about 0.4% to about 6%, or from about 0.4%to about 5%, and any ranges and sub-ranges between the foregoing values.In one or more embodiments, the coated article 100 exhibits an averagelight transmission of about 50% or greater, 60% or greater, 70% orgreater, 80% or greater, 90% or greater, 92% or greater, 94% or greater,96% or greater, 98% or greater, or 99% or greater, and any ranges andsub-ranges between the foregoing values, over an optical wavelengthregime. In embodiments, the coated article 100 may exhibit a lighttransmission in the range from about 99.5 to about 90%, 92%, 94%, 96%,98%, or 99%, and any ranges and sub-ranges between the foregoing values.

In some embodiments, the coated article 100 may exhibit an averagevisible photopic reflectance of about 50% or less, 40% or less, 30% orless, 20% or less, 10% or less, about 9% or less, about 8% or less,about 7% or less, about 6% or less, about 5% or less, about 4% or less,about 3% or less, about 2% or less, about 1% or less, or even about 0.8%or less, and any ranges and sub-ranges between the foregoing values,over an optical wavelength regime. As used herein, photopic reflectancemimics the response of the human eye by weighting the reflectance versuswavelength spectrum according to the human eye's sensitivity. Photopicreflectance may also be defined as the luminance, or tristimulus Y valueof reflected light, according to known conventions such as CIE colorspace conventions. The average photopic reflectance is defined in thebelow equation as the spectral reflectance, R(λ) multiplied by theilluminant spectrum, I(λ) and the CIE's color matching function y(λ),related to the eye's spectral response

$\left\langle R_{p} \right\rangle = {\int_{380\mspace{11mu}{nm}}^{720\mspace{11mu}{nm}}{{R(\lambda)} \times {I(\lambda)} \times {\overset{¯}{y}(\lambda)}d\lambda}}$

In some embodiments, the article 100 may exhibit an average visiblephotopic transmission of about 50% or greater, 60% or greater, 70% orgreater, 80% or greater, about 85% or greater, about 90% or greater,about 92% or greater, about 94% or greater, about 96% or greater, oreven about 98% or greater, and any ranges and sub-ranges between theforegoing values, over an optical wavelength regime. Similarly, photopictransmission can be determined by the equation:

$\left\langle T_{p} \right\rangle = {\int_{380\mspace{11mu}{nm}}^{720\mspace{11mu}{nm}}{{T(\lambda)} \times {I(\lambda)} \times {\overset{¯}{y}(\lambda)}d\lambda}}$

In one or more embodiments, the coated article 100 exhibits a measurablecolor (or lack thereof) in reflectance and transmittance in the CIEL*a*b* colorimetry system (referred to herein as a “color coordinate”).The transmittance color coordinates refer to the observed L*a*b* colorcoordinates in transmittance and the reflectance color coordinates referto the observed L*a*b* color coordinates in reflectance. Thetransmittance color coordinates or reflectance color coordinates may bemeasured under a variety of illuminant light types, which may includestandard illuminants as determined by the CIE, including A illuminants(representing tungsten-filament lighting), B illuminants (daylightsimulating illuminants), C illuminants (daylight simulatingilluminants), D series illuminants (representing natural daylight), andF series illuminants (representing various types of fluorescentlighting)). Specific illuminants include F2, F10, F11, F12 or D65, asdefined by CIE. Additionally, the reflectance color coordinates andtransmittance color coordinates may be measured at different observedangles of incidence, such as normal (0 degrees), 5 degrees, 10 degrees,15 degrees, 30 degrees, 45 degrees, or 60 degrees.

In one or more embodiments, the coated article 100 has a* of less thanor equal to about 10, 8, 6, 5, 4, 3, 2, or even 1, and any ranges andsub-ranges between the foregoing values, in transmittance and/orreflectance when viewed at a normal angle of incidence, or an angle ofincidence of 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees,or 60 degrees. In one or more embodiments, the coated article 100 has b*of less than or equal to about 10, 8, 6, 5, 4, 3, 2, or even 1, and anyranges and sub-ranges between the foregoing values, in transmittanceand/or reflectance when viewed at a normal angle of incidence, or anangle of incidence of 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45degrees, or 60 degrees. In one or more embodiments, the coated article100 has a* of greater than or equal to about −10, −8, −6, −5, −4, −3,−2, or even −1, and any ranges and sub-ranges between the foregoingvalues, in transmittance and/or reflectance when viewed at a normalangle of incidence, or an angle of incidence of 5 degrees, 10 degrees,15 degrees, 30 degrees, 45 degrees, or 60 degrees. In one or moreembodiments, the coated article 100 has b* of greater than or equal toabout −10, −8, −6, −5, −4, −3, −2, or even −1, and any ranges andsub-ranges between the foregoing values, in transmittance and/orreflectance when viewed at a normal angle of incidence, or an angle ofincidence of 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees,or 60 degrees.

In one or more embodiments, a reference point color shift may bemeasured between a reference point and the transmittance colorcoordinates or reflectance color coordinates. The reference point colorshift measures the difference in color between a reference point colorcoordinate and an observed color coordinate (either reflected ortransmitted). The reflectance reference point color shift (sometimesreferred to as the reference point color shift in reflectance) refers tothe difference between the reflected color coordinate and the referencepoint. The transmittance reference point color shift (sometimes referredto as the reference point color shift in transmittance) refers to thedifference between the transmitted color coordinates and the referencepoint. To determine the reference point color shift, a reference pointis chosen. According to embodiments described herein, the referencepoint may be the origin in the CIE L*a*b* colorimetry system (the colorcoordinates a*=0, b*=0), the coordinates (a*=−2, b*=−2), or thetransmittance or reflectance color coordinates of the substrate. Itshould be understood that unless otherwise noted, the L* coordinate ofthe articles described herein are the same as the reference point and donot influence color shift. Where the reference point color shift of thearticle is defined with respect to the substrate, the transmittancecolor coordinates of the article are compared to the transmittance colorcoordinates of the substrate and the reflectance color coordinates ofthe article are compared to the reflectance color coordinates of thesubstrate. Unless otherwise noted, the reference point color shiftrefers to the shift measured between the reference point and the colorcoordinate in transmittance or reflectance as measured at a normal anglerelative to the air-side surface 122 of the coated article 100. However,it should be understood that the reference point color shift may bedetermined based on non-normal angles of incidence, such as 5 degrees,10 degrees, 15 degrees, 30 degrees, 45 degrees, or 60 degrees.Additionally, unless otherwise noted, the reflectance color coordinatesare measured on only the air-side surface 122 of the article. However,the reflectance color coordinates described herein can be measured onboth the air-side surface 122 of the article and the opposite side ofthe article (i.e., major surface 114 in FIG. 1 ) using either a2-surface measurement (reflections from two sides of an article are bothincluded) or a 1-surface measurement (reflection from only the air-sidesurface 122 of the article is measured). Of these, the 1-surfacereflectance measurement is typically the more challenging metric toachieve low reference point color shift values for anti-reflectivecoatings, and this has relevance to applications (such as smartphones,etc.) where the back surface of the article is bonded to a lightabsorbing medium such as black ink or an LCD or OLED device).

Where the reference point is the color coordinates a*=0, b*=0 (theorigin), the reference point color shift is calculated by the followingequation: reference point colorshift=√((a*_(article))²+(b*_(article))²).

Where the reference point is the color coordinates a*=−2, b*=−2, thereference point color shift is calculated by the following equation:reference point color shift=√((a*_(article)+2)² (b*_(article)+2)²).

Where the reference point is the color coordinates of the substrate, thereference point color shift is calculated by the following equation:reference point color shift=√((a*_(article)−a*_(substrate))(b*_(article) b*_(substrate))²).

In one or more embodiments, the reference point color shift inreflectance and/or transmittance is less than about 10, less than about9, less than about 8, less than about 7, less than about 6, less thanabout 5, less than about 4, less than about 3, less than about 2.5, lessthan about 2, less than about 1.8, less than about 1.6, less than about1.4, less than about 1.2, less than about 1, less than about 0.8, lessthan about 0.6, less than about 0.4, or even less than about 0.25, andany ranges and sub-ranges between the foregoing values, as measuredrelative to one of the disclosed reference points.

Some embodiments of this disclosure pertain to a coated article 100 thatexhibits colorlessness in reflectance and/or transmittance even whenviewed at a non-normal angle of incidence under an illuminant. In one ormore embodiments, the coated articles 100 described herein may have aminimal change in visible color in reflectance and/or transmission whenthe viewing angle is changed. Such can be characterized by the angularcolor shift of a coated article 100 in reflectance or transmittance.Angular color shift may be determined using the following equation,where: angular color shift=√((a*₂−a*₁)²+(b*₂−b*₁)²). In the angularcolor shift equation, a*i, and b*i represent the a* and b* coordinatesof the article when viewed at an incidence reference illumination angle(which may include normal incidence) and a*2, and b*2 represent the a*and b* coordinates of the article when viewed at an incidentillumination angle, provided that the incident illumination angle isdifferent from the reference illumination angle and in some casesdiffers from the reference illumination angle by about 1 degree or more,for example 2 degrees or about 5 degrees. It should be understood thatunless otherwise noted, the L* coordinate of the articles describedherein are the same at any angle or reference point and do not influencecolor shift.

The reference illumination angle may include normal incidence (i.e., 0degrees), or, for example, 5 degrees, 10 degrees, 15 degrees, 30degrees, 45 degrees, or 60 degrees from normal incidence. However,unless stated otherwise, the reference illumination angle is a normalangle of incidence. The incident illumination angle may be, for example,about 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, or 60degrees from the reference illumination angle.

In one or more embodiments, the coated article 100 has an angular colorshift in reflectance and/or transmittance of about 10 or less (e.g., 5or less, 4 or less, 3 or less, or 2 or less, and any ranges andsub-ranges between the foregoing values) when viewed at a particularincident illumination angle different from a reference illuminationangle, under an illuminant. In some embodiments, the angular color shiftin reflectance and/or transmittance is about 1.9 or less, 1.8 or less,1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 orless, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 orless, and any ranges and sub-ranges between the foregoing values. Insome embodiments, the angular color shift may be about 0. The illuminantcan include standard illuminants as determined by the CIE, including Ailluminants (representing tungsten-filament lighting), B illuminants(daylight simulating illuminants), C illuminants (daylight simulatingilluminants), D series illuminants (representing natural daylight), andF series illuminants (representing various types of fluorescentlighting). In specific examples, the articles exhibit an angular colorshift in reflectance and/or transmittance of about 2 or less when viewedat incident illumination angle from the reference illumination angleunder a CIE F2, F10, F11, F12 or D65 illuminant, or more specifically,under a CIE F2 illuminant.

In one or more embodiments, the coated article 100 has an angular colorshift in reflectance and/or transmittance of about 10 or less (e.g., 5or less, 4 or less, 3 or less, or 2 or less) at all incidentillumination angles in a given range relative to the referenceillumination angle. For example, the coated article 100 may have anangular color shift of about 10 or less, 5 or less, 4 or less, 3 orless, or 2 or less at all incident illumination angles in a range fromthe reference illumination angle to about 5 degrees, 10 degrees, 15degrees, 30 degrees, 45 degrees, or 60 degrees from the referenceillumination angle. In additional embodiments, the coated article 100may have an angular color shift of about 1.9 or less, 1.8 or less, 1.7or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 orless, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 orless, and any ranges and sub-ranges between the foregoing values, at allincident illumination angles in a range from the reference illuminationangle to about 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45degrees, or 60 degrees from the reference illumination angle.

In one or more embodiments, the coated article 100 exhibits a haze valueof about 10% of less, as measured on the abraded side using a hazemetersupplied by BYK Gardner under the trademark Haze-Gard Plus®, using anaperture over the source port, the aperture having a diameter of 8 mm.In some embodiments, the haze may be about 50% or less, about 25% orless, about 20% or less, about 15% or less, about 10% or less, about 9%or less, about 8% or less, about 7% or less, about 6% or less, about 5%or less, about 4% or less, about 3% or less, about 2% or less, about 1%or less, about 0.5% or less or about 0.3% or less, and any ranges andsub-ranges between the foregoing values. In some specific embodiments,the article 100 exhibits a haze in the range from about 0.1% to about10%, from about 0.1% to about 9%, from about 0.1% to about 8%, fromabout 0.1% to about 7%, from about 0.1% to about 6%, from about 0.1% toabout 5%, from about 0.1% to about 4%, from about 0.1% to about 3%, fromabout 0.1% to about 2%, from about 0.1% to about 1%, 0.3% to about 10%,from about 0.5% to about 10%, from about 1% to about 10%, from about 2%to about 10%, from about 3% to about 10%, from about 4% to about 10%,from about 5% to about 10%, from about 6% to about 10%, from about 7% toabout 10%, from about 1% to about 8%, from about 2% to about 6%, fromabout 3% to about 5%, and all ranges and sub-ranges therebetween.

The coated articles disclosed herein may be incorporated into anotherarticle such as an article with a display (or display articles) (e.g.,consumer electronics, including mobile phones, tablets, computers,navigation systems, wearable devices (e.g., watches) and the like),architectural articles, transportation articles (e.g., automotive,trains, aircraft, sea craft, etc.), appliance articles, or any articlethat requires some transparency, scratch-resistance, abrasion resistanceor a combination thereof. An exemplary article incorporating any of thecoated articles disclosed herein is shown in FIGS. 7A and 7B.Specifically, FIGS. 7A and 7B show a consumer electronic device 700including a housing 702 having front 704, back 706, and side surfaces708; electrical components (not shown) that are at least partiallyinside or entirely within the housing and including at least acontroller, a memory, and a display 710 at or adjacent to the frontsurface of the housing; and a cover substrate 712 at or over the frontsurface of the housing such that it is over the display. In someembodiments, the cover substrate 712 may include any of the coatedarticles disclosed herein. In some embodiments, at least one of aportion of the housing or the cover glass comprises the coated articlesdisclosed herein.

EXAMPLES

The various embodiments of coated articles will be further clarified bythe following examples. The examples are illustrative in nature, andshould not be understood to limit the subject matter of the presentdisclosure.

Example 1

Films were deposited onto glass substrates by plasma deposition. Filmswere deposited onto Gorilla® Glass (Corning code #5318 having a CS ofabout 850 MPa, and a DOC of about 40 microns, and a thickness of 1.0millimeter (mm)) using reactive sputtering deposition. The sputteringtargets were 3 inch diameter targets of silicon and aluminum. Eachtarget had a pneumatically driven shutter which could either preventdeposition of the sputtered material when the shutter was closed, orallow deposition of the sputtered material onto the substrates when theshutter was opened. The samples are located above the sputteringtargets. The sputtering throw distance in the chamber was about 100 mm.The samples were rotated above the sputtering targets in order toimprove uniformity. A thermocouple disposed near the substrate holderwas used for monitoring temperature near (˜1 mm away) the substrate. Thesamples were heated and controlled to hold at 200° C. inside the chamberprior to, and during deposition. The chamber used a variable angle gatevalve for controlling the pressure. This variable angle valve is aconvenience, but is not required to achieve the film properties that aredisclosed herein. The deposition chamber used a load lock for transportof the samples into the chamber. The chamber was pumped via aturbomolecular pump. The base pressure of the chamber was about 0.1microtorr (i.e. le-7 torr).

A deposition run was started by loading the samples into the load lock,pumping down the load lock, and then transferring the samples into thedeposition chamber. A flow of argon gas was started in the depositionchamber and the variable angle gate valve was used to control thepressure to about 30 millitorr. After a pressure of about 30 millitorrstabilized, a plasma was then started at each of the sputter targetsthat were intended to be used for the coating run. The plasma was drivenby either or both of DC and RF (13.56 MHz) power. Typically there wasused 300 watts of DC superimposed with 200 watts of RF on a 99.99% purealuminum target, and 500 watts of DC on the p-doped Si target, butvariations are shown in Table 1. Subsequent experiments have found thatthe Al could also be driven with 500 watts of DC alone, with nosuperimposed RF. After the plasma stabilized for about a minute, thepressure was reduced to a deposition pressure using the variable anglegate valve.

After the plasma was stabilized at the deposition pressure, oxidants;nitrogen and oxygen gas were introduced. Typically, there was used a 30standard cubic centimeter per minute (sccm) flow of N2, and about 0.5sccm of oxygen. These values also changed from one deposition run toanother, as shown in Table 1. Some deposition runs used no oxygen, andsome used up to 3 sccm of oxygen. The introduction of the oxidant gassespartially poisoned the sputter target surfaces with nitrogen and oxygen,as could be seen by the decrease in voltage on the power supplies to themagnetrons. The exact degree of poisoning was not known. After a shortstabilization time of about a minute, the shutters to the magnetrontargets were opened, allowing the sputtered material to deposit onto thesamples.

Table 1 shows deposition conditions for the various samples of Example1.

TABLE 1 Ar N2 O2 Al RF Al DC Si RF Deposition Deposition Flow flow flowpower power power pressure Substrate Sample # time (s) (sccm) (sccm)(sccm) (W) (W) (W) (mT) Bias (V) Sample 1 4128 20 30 0.25 240 300 500 240 Sample 2 9000 30 30 0.5 200 300 500 2 0 Sample 3 9000 20 40 0.5 160240 0 1.5 40 Sample 4 9000 15 30 0.25 240 160 550 2.5 40 Comparative9000 30 30 0.25 200 300 50 3 40 Sample A Comparative 9000 30 30 0.25 200300 0 4 40 Sample B Comparative 9000 20 15 0.5 220 330 0 1.5 0 Sample CComparative 9000 25 27.5 0.37 190 285 275 3.25 20 Sample D

Table 2 shows the compositions of the coatings produced in Example 1.

TABLE #2 Sample # N O Al Si Sample 1 46.84 1.67 30.54 20.96 Sample 243.84 4.67 28.20 23.28 Sample 3 32.41 15.96 51.62 0.00 Sample 4 45.683.82 24.76 25.74 Comparative 37.38 10.27 52.36 0.00 Sample A Comparative36.91 10.37 52.72 0.00 Sample B Comparative 38.46 9.17 52.37 0.00 SampleC Comparative 42.99 5.66 39.20 12.15 Sample D

Table 3 depicts properties as measured for the coatings of Example 1.Specifically, Table 3 shows coating thickness, strain-to-failure of thecoating (for the coating residing on the substrate), strain-to-failureof the substrate (for the substrate as tested with the coating residingthereon), modulus (E) as measured for the coating residing on thesubstrate, hardness (H) as measured for the coating residing on thesubstrate, and the film stress (residual stress in the film) as measuredusing the techniques described above. The same conventions andaforementioned notes with respect to Table #3 were also used for theresults reported in Table #4 below.

TABLE 3 Film stress Coating Coating Substrate (Mpa) thickness strain tofailure strain to failure (+ is tensile, Sample # (nm) (%) (%) E (GPa) H(GPa) − is compressive) Sample 1 558 0.74 0.74 211 18 −500 Sample 2 11600.72 0.72 228 19.8 −960 Sample 3 408 0.73 0.73 173 17.5 −442 Sample 4855 0.73 0.73 200 17.4 −828 Comparative 460 0.59 0.99 188 17.8 147Sample A Comparative 468 0.62 0.97 223 17 399 Sample B Compamtive 11520.31 0.35 229 20.9 479 Sample C Comparative 726 0.38 0.38 198 17.5 −5Sample D

As shown in Table #3, films with residual compressive stress (forexample, 5 MPa or more, more than 50 MPa, more than 100 MPa, more than150 MPa, more than 200 MPa, more than 400 MPa, 500 MPa or more, morethan 800 MPa, and more than 900 MPa, wherein a negative sign in thetables denotes compressive stress) did not crack prior to the failure ofthe substrate. That is, the coating and the substrate had the samestrain to failure, i.e., they failed under the same load. Because thematerials involved are brittle, and because the substrate thickness ismuch greater than that of the coating, when the substrate fails, thecoating will fail along with it. Thus, when coating strain to failureequals substrate strain to failure, the coating was at least as robustas the substrate. In some instances, it is beneficial to have thecoating and substrate be of similar robustness, i.e., fail at a similarstrain to failure. However, in some instances, more desirable thanachieving similar strain to failure between the coating and thesubstrate, is achieving a high strain to failure for each of the coatingand substrate even if they are not similar to one another. That is, whenboth the substrate and coating have a high strain to failure, theproduct including such a coated substrate will be more durable in termsof applied load and flexure than a product including a coated substratewherein strain to failure is similar between coating and substrate, butis low. Also, strain to failure is dependent upon the thickness of thecoating and the thickness of the substrate. In Tables #3 and 4, the samesubstrate thickness was used throughout.

Thus, for example, comparing Comparative Sample D and Sample 6, whichhave similar coating thicknesses (726 nm and 720 nm, respectively),Sample 6 is more desirable because the coating strain to failure ishigher than that in Comparative Sample D (0.61% versus 0.38%,respectively), even though the coating strain to failure in ComparativeSample D is similar to that of the substrate (0.38% for each), whereasthe coating strain to failure of Sample 6 is lower than that of thesubstrate (0.61% versus 0.78%, respectively). Taking the comparison ofthese Samples further, the residual compressive stress in Sample 6(about 200 MPa) is higher than that in Comparative Sample D (about 5MPa), which leads to the higher coating strain to failure, and a moredesirable coated substrate. That is, controlling the residual stress inthe coating, particularly controlling the residual stress to becompressive, and more particularly controlling the residual stress to beof a sufficient level of compression, is desirable in increasing thestrain to failure of the coating.

For example, Sample 2 and Comparative Sample C have about the samethickness (1160 nm versus 1152 nm), modulus (228 GPa versus 229 GPa),and hardness (19.8 GPa versus 20.9 GPa), but because of the higherresidual compressive stress in Sample 2 (960 MPa versus a tensileresidual stress of 479 MPa in Comparative Sample C), the Sample 2coating strain to failure is much higher than that of Comparative SampleC (0.72% versus 0.31%).

Similarly, Sample 4 is preferred over Comparative Sample D because ithas a higher strain to failure (0.73% versus 0.38%) for both coating andsubstrate, wherein these samples have similar hardness (17.4 GPa versus17.5 GPa, respectively), and similar modulus (200 GPa versus 198 GPa,respectively). Again, it is seen that the higher compressive stress inSample 4 (828 MPa versus the 5 MPa for Comparative Sample D) leads tothe higher strain to failure (0.73% versus 0.38% of Comparative SampleD). Although Sample 4 had a somewhat higher thickness than that ofComparative Sample D (855 nm versus 726 nm, respectively), one wouldexpect that the thinner coating would produce a higher strain to failure(for the same coating residual compressive stress) as shown in Table #4of Example 2.

Example 2

Coatings were deposited onto Gorilla® Glass (Corning code #5318 having aCS of about 850 MPa, and a DOC of about 40 microns, and a thickness of1.0 mm) using ion assisted plasma deposition utilizing a TecportSymphony deposition device. Table 4 depicts the conditions for thedeposition. All coatings of Example 2 were formed from AlON. The powerapplied to the Al magnetron during deposition was 4 kW. Deposition timesvaried, as shown in the Table 4. The argon flow applied to the magnetronwas 40 sccm, and the argon flow applied to the ion gun was 25 sccm. Thenitrogen flow applied to the ion gun was 45 sccm, and the oxygen flowapplied to the ion gun was 2.5 sccm. Pumping for the deposition utilized2 cyro pumps for 1.39 mT chamber pressure. The samples were rotated at20 rpm. Table 4 also shows modulus and hardness for the samples, as wellas the coated substrate strain-to failure.

TABLE 4 Coating Substrate Deposition thickness strain to failure failurestrain Sample # time (s) (nm) stress E (GPa) H (Gpa) (%) (%) Sample 510800 1090 −234.3 127 13.1 0.42 0.81 Sample 6 7200 720 −185.4 180 15.30.61 0.78 Sample 7 3600 370 −197.8 162 14.1 0.8 0.8

From Example 2, Samples 5-7, it is seen that for a given residualcompressive stress (for example about 200 MPa) as coating thicknessdecreased from about 1000 nm to about 700 nm to about 350 nm, thecoating strain to failure increased from about 0.4% to about 0.6% toabout 0.8%

From the above Examples 1 and 2, it can be seen that: (i) for a givencoating thickness, hardness, and modulus, higher residual compressivestress in the film leads to a desirably higher strain to failure in thefilm; (ii) for a given amount of residual compressive stress in thefilm, a thinner film leads to a higher strain to failure in the film;and (iii) that a desirable level of strain to failure in the film can beachieved with coatings having a variety of hardness and modulus, whichmay thus provide a desirable degree of scratch resistance. That is,generally, the higher the modulus and the higher the hardness of thecoating, the better the scratch resistance. However, the higher themodulus and the higher the hardness, the more brittle the material willbe and, thus, the lower its strain to failure. Thus, using the conceptsin the present disclosure, one can appropriately balance coatingproperties (e.g., thickness, hardness, modulus, and residual stress) todesign a coating having a desirable scratch resistance (high hardnessand/or modulus) and durability (high strain to failure, for example highcoating strain to failure).

For example, coatings having a thickness of from about 600 nm to about1160 nm (for example, from about 700 nm to about 900 nm—See Samples 2,4, 5, and 6), and hardnesses of greater than about 12 GPa (for exampleabout 13 GPa or more, about 15 GPa or more, about 17 GPa or more, orabout 19 GPa or more—see Samples 5, 6, 4, and 2, respectively) a coatingstrain to failure of greater than or equal to about 0.42% (for example,about 0.42% or more, about 0.6% or more, about 0.7% or more—see Samples5, 6, and 2&4, respectively) can be achieved, with a residualcompressive stress of more than 5 MPa, or more than 50 MPa, or more than100 MPa (for example, more than 150 MPa, more than 200 MPa, more than800 MPa, and more than 900 MPa—see Samples 6, 5, 4, and 2,respectively). Similarly, for example, coatings having a thickness offrom about 300 nm to about 600 nm (for example, about 350 nm or more,400 nm or more, or about 550 nm or more—see Samples 7, 3, and 1,respectively), and hardnesses of greater than or equal to about 14 GPa(for example 14 GPa or more, about 17 GPa or more, or about 18 GPa ormore—see Samples 7, 3, and 1, respectively) a coating strain to failureof greater than about 0.65 (for example greater than about 0.7, about0.74 or more, about 0.8 or more—see Samples 3, 1, and 7, respectively)can be achieved, with a residual compressive stress of more than 5 MPaor more than 50 MPa, or more than 75 MPa, or more than 100 MPa (forexample, 200 MPa or more, more than 400 MPa, and 500 MPa or more—seeSamples 7, 3, and 1, respectively).

As can be seen in the Table 3, for coated articles having a coating with1 um thickness or greater and a (coating or article) hardness greaterthan 12, 14, 16, or 18 GPa, the coating strain-to-failure can beundesirably as low as 0.31 (see Comparative Sample C) when the filmstress is not carefully controlled, i.e., when the residual film stressis not sufficiently compressive. For this same coating thickness andhardness range, the coating strain to failure can be greater than 0.4,greater than 0.5, greater than 0.6, or greater than 0.7 when film stressis well controlled, i.e., residual film stress is controlled to becompressive, for example to have a residual compressive stress of morethan 5 MPa, or more than 50 MPa, or more than 100 MPa, or more than 150MPa, or more than 200 MPa, or more than 250 MPa, or more than 300 MPa,or more than 350 MPa, or more than 400 MPa, or more than 450 MPa, ormore than 500 MPa, or more than 550 MPa, or more than 600 MPa, or morethan 650 MPa, or more than 700 MPa, or more than 750 MPa, or more than800 MPa, or more than 850 MPa, or more than 900 MPa, or more than 950MPa.

Additionally, for coated articles having a coating in a thickness rangeof 600-1000 nm or 700-900 nm, with a hardness greater than 12, 14, or 16GPa, coating strain-to-failure can be as low as 0.38 (as shown inComparative Sample D) when film stress is not well controlled, i.e.,when the residual film stress is not sufficiently compressive, butstrain-to-failure can be greater than 0.45, greater than 0.55, greaterthan 0.65, or greater than 0.7 when film stress is well controlled,i.e., residual film stress is controlled to be compressive, for exampleto have a residual compressive stress of more than 5 MPa, or more than50 MPa, or more than 100 MPa, or more than 150 MPa, or more than 200MPa, or more than 250 MPa, or more than 300 MPa, or more than 350 MPa,or more than 400 MPa, or more than 450 MPa, or more than 500 MPa, ormore than 550 MPa, or more than 600 MPa, or more than 650 MPa, or morethan 700 MPa, or more than 750 MPa, or more than 800 MPa, or more than850 MPa, or more than 900 MPa, or more than 950 MPa.

For coated articles having a coating in a thickness range of 400-600 nm,with a hardness greater than 12, 14, or 16 GPa, coatingstrain-to-failure can be as low as 0.59 (see Comparative Sample A) whenfilm stress is not well controlled, but coating strain to failure can begreater than 0.65 or greater than 0.7 when film stress is wellcontrolled, i.e., residual film stress is controlled to be compressive,for example to have a residual compressive stress of more than 5 MPa, ormore than 50 MPa, or more than 100 MPa, or more than 150 MPa, or morethan 200 MPa, or more than 250 MPa, or more than 300 MPa, or more than350 MPa, or more than 400 MPa, or more than 450 MPa, or about 500 MPa ormore.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. When the term “about” is used in describing a value oran end-point of a range, the disclosure should be understood to includethe specific value or end-point referred to. Whether or not a numericalvalue or end-point of a range in the specification recites “about,” thenumerical value or end-point of a range is intended to include twoembodiments: one modified by “about,” and one not modified by “about.”It will be further understood that the endpoints of each of the rangesare significant both in relation to the other endpoint, andindependently of the other endpoint.

The terms “substantial,” “substantially,” and variations thereof as usedherein are intended to note that a described feature is equal orapproximately equal to a value or description. For example, a“substantially planar” surface is intended to denote a surface that isplanar or approximately planar. Moreover, “substantially” is intended todenote that two values are equal or approximately equal. In someembodiments, “substantially” may denote values within about 10% of eachother, such as within about 5% of each other, or within about 2% of eachother.

Directional terms as used herein—for example up, down, right, left,front, back, top, bottom—are made only with reference to the figures asdrawn and are not intended to imply absolute orientation.

As used herein the terms “the,” “a,” or “an,” mean “at least one,” andshould not be limited to “only one” unless explicitly indicated to thecontrary. Thus, for example, reference to “a component” includesembodiments having two or more such components unless the contextclearly indicates otherwise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present disclosurewithout departing from the spirit and scope of the disclosure. Thus, itis intended that the present disclosure cover such modifications andvariations provided they come within the scope of the appended claimsand their equivalents.

What is claimed is:
 1. A coated article comprising: a substratecomprising a major surface; an optical coating disposed on the majorsurface of the substrate and forming an air-side surface, the opticalcoating comprising one or more layers of deposited material; wherein: atleast a portion of the optical coating comprises a residual compressivestress of more than 100 MPa; the coated article comprises astrain-to-failure of 0.4% or more as measured by a Ring-on-Ring TensileTesting Procedure; the optical coating comprises a maximum hardness of 8GPa or more as measured on the air-side surface by a Berkovich IndenterHardness Test along an indentation depth of 50 nm and greater; and thecoated article comprises an average photopic transmission of 50% orgreater.
 2. The coated article of claim 1, wherein at least a portion ofthe optical coating comprises a residual compressive stress of more than500 MPa.
 3. The coated article of claim 1, wherein: the optical coatingcomprises a maximum hardness of 12 GPa or more as measured on theair-side surface by a Berkovich Indenter Hardness Test along anindentation depth of 50 nm and greater; and the optical coatingcomprises a physical thickness of 1 micron or greater.
 4. The coatedarticle of claim 1, wherein the coated article comprises an averagephotopic transmission of 80% or greater.
 5. The coated article of claim1, wherein the substrate comprises glass or glass-ceramic.
 6. The coatedarticle of claim 1, wherein the substrate is chemically strengthened. 7.The coated article of claim 1, wherein the optical coating is a singlelayer.
 8. The coated article of claim 1, wherein the optical coatingcomprise two or more layers.
 9. The coated article of claim 1, whereinthe optical coating comprises a gradient layer, wherein the gradientlayer changes in composition, refractive index, or both.
 10. The coatedarticle of claim 1, wherein: the optical coating further comprises ascratch-resistant layer; and the gradient layer is positioned betweenthe substrate and the scratch-resistant layer.
 11. The coated article ofclaim 1, wherein the optical coating comprises SiO_(x)N_(y).
 12. Aconsumer electronic product, comprising: a housing having a frontsurface, a back surface and side surfaces; electrical componentsprovided at least partially within the housing, the electricalcomponents including at least a controller, a memory, and a display, thedisplay being provided at or adjacent the front surface of the housing;and a cover glass disposed over the display, wherein at least one of aportion of the housing or the cover glass comprises the coated articleof claim
 1. 13. A method for making a coated article, the methodcomprising: depositing an optical coating onto a major surface of asubstrate, the optical coating forming an air-side surface andcomprising one or more layers of deposited material; wherein: at least aportion of the optical coating comprises a residual compressive stressof more than 100 MPa; the coated article comprises a strain-to-failureof 0.4% or more as measured by a Ring-on-Ring Tensile Testing Procedure;the optical coating comprises a maximum hardness of 8 GPa or more asmeasured on the air-side surface by a Berkovich Indenter Hardness Testalong an indentation depth of 50 nm and greater; and the coated articlecomprises an average photopic transmission of 50% or greater.
 14. Themethod of claim 13, wherein at least a portion of the optical coatingcomprises a residual compressive stress of more than 500 MPa.
 15. Themethod of claim 13, wherein: the optical coating comprises a maximumhardness of 12 GPa or more as measured on the air-side surface by aBerkovich Indenter Hardness Test along an indentation depth of 50 nm andgreater; and the optical coating comprises a physical thickness of 1micron or greater.
 16. The method of claim 13, wherein the coatedarticle comprises an average photopic transmission of 80% or greater.17. The method of claim 13, wherein the substrate comprises glass orglass-ceramic.
 18. The method of claim 13, wherein the substrate ischemically strengthened.
 19. The method of claim 13, wherein the opticalcoating is a single layer.
 20. The method of claim 13, wherein theoptical coating comprise two or more layers.